President Barack Obama’s nominee for defense secretary on Thursday defended his views of the military and global threats to the US and its allies, pushing back against criticism that has focused on his past statements on Israel, Iran and nuclear weapons.

Chuck Hagel answered his critics by pledging to maintain Israel’s military supremacy, saying, “I will ensure our friend and ally Israel maintains its qualitative military edge in the region.”

“We will continue to support systems such as the Iron Dome, which saves Israeli lives from terrorist rocket attacks.” Hagel added.

Hagel told senators at his confirmation hearing that America “must engage — not retreat — in the world,” and insisted that his record is consistent on that point.

At the hearing, the former Republican two-term senator from Nebraska sought to defuse the barrage of criticism about his past remarks that GOP critics say showed a lack of support for Israel. Hagel sought to build support for his nomination to succeed Defense Secretary Leon Panetta.

“No one individual vote, no one individual quote or no one individual statement defines me, my beliefs, or my record,” Hagel told the Senate Armed Services Committee in prepared testimony. “My overall worldview has never changed: that 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, 66, a decorated Vietnam combat veteran, would be the first enlisted man to become defense secretary, a point that Armed Services Committee Chairman Carl Levin, D-Mich., highlighted.

“It would be a positive message for our soldiers, sailors, airmen and Marines in harm’s way around the world to know that one of their own holds the highest office in the Department of Defense and that he has their backs,” Levin said.

Hagel was the lone witness in a jam-packed hearing room at a session that could be crucial in determining whether he will win Senate confirmation and join Obama’s second-term national security team. Two former committee chairmen — Democrat Sam Nunn and Republican John Warner — introduced the nominee.

“War for Chuck Hagel is not an abstraction,” Nunn said.

Hagel has the announced backing of about a dozen Democrats and the tacit support of dozens more who are unlikely to embarrass the president by defeating his Cabinet pick. One Republican — Sen. Thad Cochran of Mississippi — has said he will vote for his former colleague.

Six Republicans, including four members of the Armed Services panel, have said they will oppose Hagel’s nomination. Sen. Jim Inhofe of Oklahoma, the top GOP lawmaker on the committee and an opponent of Hagel, almost immediately complained that Hagel had not provided to the committee all of his speeches over the last five years, as requested.

Inhofe said Hagel’s record “is deeply troubling and out of mainstream views.”

Hagel would be the lone Republican in the Obama Cabinet if the Senate confirms him, but the prospect has failed to placate GOP senators in a post-election atmosphere that remains as politically divisive as the fierce 2012 campaign.

Once the hearing was under way, the Republican National Committee put out a news release titled, “Chuck Hagel Is the Wrong Choice for Secretary of Defense,” and contending that he would weaken the nation’s military.

Responding specifically to attacks from outside GOP-leaning groups, Hagel said he was committed to Obama’s goal of ensuring that Iran does not obtain a nuclear weapon, and insisted that all options, including military force, are on the table.

“My policy is one of prevention, and not one of containment — and the president has made clear that is the policy of our government,” Hagel said.

Under questioning, Hagel said he always supported multilateral sanctions against Iran, but acknowledged that he cast votes against unilateral sanctions on a case-by-case basis. He argued that in some cases, such as votes in 2001-2002, he was taking into account the concerns of Republican president George W. Bush.

He also countered with votes and letters against Iran and Hezbollah.

“There’s a more complete record than just one or two or three or four” votes, Hagel said, insisting that he has been on the record many times saying Hamas and Hezbollah are terrorist organizations and Iran is a state sponsor of terrorism.

Responding specifically to attacks from outside GOP-leaning groups, Hagel repeated his regrets about using the term “Jewish lobby” to refer to pro-Israel groups. He said he should have used another term.

“I should have used another term and I’m sorry and I regret it,” Hagel said. “On the use of intimidation [by such groups], I should have used ‘influence,’ I think would have been more appropriate.”

He also expressed support for the US maintaining a strong, modern nuclear arsenal, a position that has been challenged because of his support for the Global Zero organization’s recommendation of nuclear cuts.

“We are not going to unilaterally disarm,” Hagel said.

Crucial for Hagel will be the questioning by Sen. John McCain, R-Ariz. Hagel and McCain are fellow Vietnam veterans who once had a close relationship during their years in the Senate, but politics and Hagel’s opposition to increased troop numbers in Iraq divided the two men.

McCain has praised Hagel’s military service but said he had serious concerns about positions the nominee has taken on various issues. He said he is reserving judgment until after the hearing. Sen. Lindsey Graham, R-S.C., earlier this month described Obama’s selection as an “in-your-face” pick, but was a bit less critical this week.

“Who are we getting — the guy today or the guy who said things before?” Graham said Tuesday after a 20-minute meeting with Hagel. Graham said he doesn’t doubt Hagel’s “personal integrity, but I do have real concerns about his policy positions.”

Hagel addressed much of the criticism lodged against him in a 112-page questionnaire to the committee in which he said his wartime experience would shape his decisions about using military force.

“I understand what it is like to be a soldier in war,” wrote Hagel. “I also understand what happens when there is poor morale and discipline among the troops and a lack of clear objectives, intelligence and command and control from Washington. I believe that experience will help me as secretary of defense to ensure we maintain the best fighting force in the world, protect our men and women in uniform and ensure that we are cautious and certain when contemplating the use of force.”

Philip Podolsky contributed to this report.