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 during the hearing, which ran several hours.
He also appeared evasive 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.
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.
Despite the campaign against him waged by conservatives, Hagel was expected to win confirmation to succeed Leon Panetta as Pentagon chief.
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.
"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. I believe, and always have believed, that America must engage in the world -- not retreat -- but engage in the world. My record is consistent on these points," he told the panel.
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 new 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, saying: "I think my record is pretty clear."
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.
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.
"I am committed to effectively and efficiently using every single taxpayer dollar the right way; to maintain the strongest military in the world; and to working with Congress to ensure the department has the resources it needs -- and the disposition of those resources is accountable," he said.
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 enlisted man to serve as defense secretary. He was an Army sergeant in Vietnam, where he was wounded, and he conceded 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."
Hagel also declared that he would be prepared to deploy the military unilaterally and as part of an allied effort, if necessary.
"I think we need to be cautious with our power," he said, adding that he believed no nation in history has "ever been as judicious and careful with that power as we have."
On the eve of his hearing, Hagel received the endorsement of seven prominent veterans groups, including Veterans of Foreign Wars and the American Legion.
In its letter of endorsement, the Iraq and Afghanistan Veterans of America said of Hagel, "As a former enlisted soldier, Senator Hagel understands the challenges our troops and veterans face on a deeply personal level."
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.
Under persistent hammering by Sen. Lindsey Graham, R-South Carolina, Hagel conceded that he never should have made the comment about the Jewish lobby.
Hagel has met with 60 senators and has appointments to meet with more next week to go over issues related to his nomination. Only one Republican senator so far has endorsed his appointment. The office of Sen. Thad Cochran confirmed to CNN that the Mississippi lawmaker plans to vote to confirm Hagel.
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.
The CNN poll indicated a partisan divide, with nearly two-thirds of Democrats saying Hagel should be confirmed. That number drops to 44% among independents and 32% among Republicans.
The CNN poll was in line with an ABC News/Washington Post poll that was conducted a few days earlier.