Washington (CNN) -- Former Sen. Chuck Hagel took on critics at his Senate confirmation hearing on Thursday to become President Barack Obama's next defense secretary, saying he may have been wrong at times in the past but always acted in the nation's best interests.
Facing tough questioning from conservatives, the decorated Vietnam veteran told the Senate Armed Services Committee that he fully supported Obama administration policies on ending combat operations in Afghanistan next year, preventing Iran from obtaining a nuclear weapon, and ending the ban on gays openly serving in the military.
However, Hagel stumbled at times and conceded toward the end of the seven hours of testimony that past statements on volatile issues such as the Middle East conflict and sanctions against Iran no longer applied or had been poorly expressed in the first place.
"If I had an opportunity to edit that, like many things I said, I would like to go back and change the words and meaning," Hagel responded at one point to a question about a 2003 comment in which he referred to Israel keeping people "like caged animals."
At another point at the contentious hearing, he referred to Iran as a legitimate state, causing Democratic Sen. Kirsten Gillibrand of New York to suggest he meant to say it was a recognized government.
"What I meant to say, should have said is - it is recognizable," Hagel said. "It has been recognized, is recognized at the United Nations. Most of our allies have embassies there. That is what I should have said and thank you."
He also appeared evasive early on when confronted by some former Senate colleagues who challenged his nomination because of what they characterized as shifting positions on confronting Iran, supporting Israel and maintaining a strong military amid pressure to cut costs.
Later in the day, Hagel sounded more certain in responding to the repeated challenges by conservatives over what newly elected Sen. Ted Cruz of Texas called his record of "antagonism" toward Israel.
Chuck Hagel's other war 
McCain and Hagel's complicated history Despite the campaign against him waged by conservatives, Hagel was expected to win confirmation to succeed Leon Panetta as Pentagon chief.
Other prominent political figures endorsed him, including former Sen. Sam Nunn, a conservative Democrat from Georgia and respected defense and nuclear policy expert, and former Sen. John Warner, a conservative Republican from Virginia, where the Pentagon is located and key military installations are based.
In his opening statement and in response to questions, Hagel defended his 12-year record as a Republican senator from Nebraska and what he called a consistent worldview on the role of the United States and its unparalleled military might.
Old friends McCain and Hagel spar at hearing
"America has and must maintain the strongest military in the world; that we must lead the international community to confront threats and challenges together; and that we must use all tools of American power to protect our citizens and our interests," Hagel said, adding that the United States must engage the world.
Obama is reassembling his national security team at the start of his second term, turning to Vietnam War heroes for marquee positions: Hagel at defense and Sen. John Kerry to lead the State Department.
The next defense chief will wind down the war in Afghanistan and face fluid issues related to Iran and the civil war in Syria. Emerging terror hotspots in Africa and managing the Pentagon through budget uncertainty are other top priorities.
On specific issues at the hearing, Hagel said he was committed to Obama's goal of preventing Iran from obtaining a nuclear weapon.
"I've been on record on that issue. And as I've said in the past many times, all options must be on the table to achieve that goal. My policy is one of prevention, and not one of containment -- and the president has made clear that is the policy of our government," he said.
Armed Services Chairman Carl Levin, D-Michigan, told Hagel that "your reassurance to me in my office that you support the Obama administration's strong stance against Iran is significant."
However, the panel's top Republican, Sen. James Inhofe of Oklahoma, said he would oppose the nomination because of what he called Hagel's past support for policies that he said would appease U.S. enemies.
In particular, Inhofe cited Hagel's backing of direct talks with Iran, an enemy of Israel. Others challenged a Senate vote by Hagel years earlier to oppose unilateral U.S. sanctions against Iran, and a comment about the "Jewish lobby" in Washington that critics said hinted at anti-Israel sentiments.
Hagel, however, pledged continued support to help Israel's military prowess in the region. In response to repeated questions about his commitment to Israel, Hagel cited his Senate record of voting for every aid authorization or other measure supporting Israel.
"I think my record is pretty clear," he said.
In addition, Hagel said the United States was "not going to unilaterally disarm" when questioned about his ties to a group calling for eliminating nuclear weapons. If confirmed, he said, he would maintain "a modern, strong, safe, ready, and effective nuclear arsenal," adding that he was "committed to modernizing" it.
Is this a 'strategy'? Why some conservatives are still going after Hagel
Regarding the possibility of impending budget cuts described by some as potentially devastating to Pentagon operations and the civilian economy it supports, Hagel said he would keep defense forces strong through efficient use of taxpayer dollars.
Asked later about the impact of the possible cuts, Hagel said that "the security of this country is not going to be in jeopardy." But he added that "if this happens, it's going to be a severe problem."
The military faces $500 billion in automatic spending cuts over the next decade absent congressional intervention in coming months to avert or soften them. This would come on top of steep budget reductions already in the pipeline.
If confirmed, Hagel will be the first defense secretary to have served all of his military career as an enlisted soldier. He was an Army sergeant in Vietnam, where he was wounded, and said on Thursday that his war experience was an influence in his life.
"I'm not shaped, framed, molded, consumed by that experience, but it's part of me," Hagel said, adding that he thought it would be a positive to have the defense secretary for the first time be someone "who understands the reality and consequences of war."
Avlon: A reality check for Chuck Hagel bashers
A sharp exchange on Thursday came when Sen. John McCain criticized Hagel's opposition to the troop surge in Iraq by the Bush administration and a similar move by Obama in Afghanistan. Both were crucial wartime decisions made by policymakers.
McCain, a former naval aviator and prisoner of war in Vietnam, said Hagel was wrong on both counts. The Arizona Republican said that he and Hagel, who once were close political allies and personal friends, had "fundamental differences" on important issues.
Hagel responded that his questioning of the surge strategy in Iraq was not an aberration.
"I always ask the question is this going to be worth the sacrifice because there will be sacrifice," Hagel said. "Now, was it required? Was it necessary? Senator McCain has his own opinion on that, shared by others. I am not sure. I am not that certain that it was required. It doesn't mean I am right."
Other Republicans on the panel complained that Hagel failed to turn over requested copies of past speeches and financial reports they requested, and he avoided directly answering some questions seeking to force him to declare that previous positions or comments were mistaken.
Hammered during questioning by Sen. Lindsey Graham, R-South Carolina, Hagel conceded that he never should have made the comment about the Jewish lobby.
Hagel had three major preparatory sessions for Thursday's hearing, according to an administration official involved in the confirmation process. The official said Hagel chose to "take the high road" by not responding with anger to "political theater."
However, another official acknowledged Hagel had some difficulty, saying "we think he's on his way, but he didn't round the bases today. He could have. He didn't."
A plurality of Americans back Hagel's nomination to succeed Panetta.
According to a CNN/ORC International poll conducted January 14-15 and released two weeks ago, 48% of the public said the Senate should confirm Hagel, with 22% saying no and three in 10 unsure.
John Mangrum returned from a vacation in early January and was greeted with about 10 inches of snow that had fallen the previous few days. "Luckily," he said, "the temperature had warmed up enough to produce some beautiful icicles hanging from the roof." 
Cindy Schultz spotted these intricate crystals in the frost outside her kitchen window. "Winter can be a beautiful time of year, as long as you bundle up!" she said. 
Ice and snow are not very common in Knoxville, Tennessee, says Sabah Moetasim, so "we tend to enjoy these situations and capture them in memories." She used a macro lens to capture this shot of icicles hanging off a backyard swing on January 25, the day a wintry mix of rain and snow hit the area. 
Caroline Newby saw a news report about the frozen formations on Paterson, New Jersey's Great Falls. She called her sister and told her, "Get dressed warm, we are going to get some photos." Newby says, "I love, love, love winter photography and will dress like an eskimo to get good photos." 
After a late January ice storm in Greenville, North Carolina, Richard Barnhill was walking around his parents' yard when he spotted this cardinal and "took as many pictures as I could." 
Stormchaser Danny Murphy spotted these icicles on his son's pickup truck as Iowa dealt with its worst ice storm since 2007. He snapped photos on January 27. 
The state experienced up to a quarter-inch of ice covering trees, power lines and roads. "We rarely get ice storms in northeast Iowa, so this is a bit unusual for us," said Murphy. 
Ice photography can be "a contact sport ... with the ground," says Kevin Cavallin, a biologist and amateur photographer in Ames, Iowa. He came close to falling a few times trying to kneel down to get a good shot of icicles on a railing. Be careful out there! 
Freezing rain in Centerville, Utah, left graphic designer Katie Poloni's car wrapped in a thin layer of ice. "We didn't know what to do. Spent an hour trying to scrape the ice off my car and gave up to write this message." 
That is quite the frozen fountain in New York's Bryant Park. Miriam Cintron heard about the spectacle January 25 on Twitter and wanted to capture the moment. "I think the frozen fountain epitomizes just how cold it has been in NYC this past week," she said. "If you spill coffee on the sidewalk, it will freeze in minutes." 
"I never saw palm trees with icicles nearby," remarked Jutka T. Emoke Barabas on this frozen fountain, which she photographed on January 14. She's been in Vegas during the winter before but says she "never saw so much ice." 
"Beauty always comes with great storms, no matter where you are," says Lee Gunderson. "When the sun comes on frozen rain or hoar frost it is always beautiful." Albany, New York Franklin, Wisconsin Knoxville, Tennessee Paterson, New Jersey Greenville, North Carolina Hazleton, Iowa Hazleton, Iowa Ames, Iowa Centerville, Utah New York Las Vegas Stettler, Alberta, Canada HIDE CAPTION << < 
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A pedestrian bundled up against the cold walks through the streets of Manhattan on Friday, January 24, in New York City. Polar air settled in over the northeastern U.S. Wednesday, with temperatures in the teens and 20s. Forecasters warned that "bitterly cold conditions" were expected across much of the Northeast, Mid-Atlantic and Mideast through this weekend. 
A surfer store with guys in swimwear seems an especially cruel sight for these bundled-up New Yorkers on Tuesday, January 22, as frigid temps hit the region. 
A lone pedestrian braves the winter chill on a Manhattan street on Thursday, January 24. 
Much of the Northeast is experiencing colder than usual temperatures, but the weather doesn't deter this woman on Wednesday, January 23, in New York. 
Ice covers firefighter Michael De Jesus while he mans a water cannon at the scene of a warehouse fire in Chicago on January 24. 
No, it's not a scene from the latest remake of "Anna Karenina," just a woman trying to ward off the cold in New York on January 22. 
A man keeps bundled up as he waits to cross the street in New York on January 23. 
A woman pulls on her gloves on January 23 in New York. 
Firefighters battle a warehouse fire in Chicago on January 24. 
A woman hails a taxi on Lexington Avenue on Manhattan's Upper East Side on January 24. 
A woman keeps covered up as steam rises from the street on January 23 in New York. 
The U.S. Capitol in Washington is blanketed with snow on January 24. The same brutal Arctic cold front that's delivered subzero temperatures across the upper Midwest and Northeast is forecast to bring ice and freezing rain to the South and Mid-Atlantic states. 
A man walks past a steam vent on Madison Avenue in Manhattan in the early morning of January 24. 
A pedestrian bundled up against the cold walks along a street in Manhattan on January 24. Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air Blast of Arctic air HIDE CAPTION << < 
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Tornado forms before reporter on scene 
25-foot ice shoves take over street 
Weather phenomenon gives snow new look