WASHINGTON — President Barack Obama will nominate former Nebraska Sen. Chuck Hagel as his next defense secretary, a senior administration official said Sunday, choosing a former Senate colleague and a decorated Vietnam veteran and signaling he’s ready for a contentious confirmation fight likely dominated by questions about Hagel’s stands on Israel and Iran.

Obama, who avoided a Capitol Hill battle by deciding not to nominate U.N. Ambassador Susan Rice as his first choice for secretary of state, went ahead with Hagel, 66, even as leading Republicans announced their opposition - though they stopped short of saying they might try to block Hagel.

Seeking to soften the ground, the White House was alerting Senate Democrats that Hagel’s selection as the successor to Defense Secretary Leon Panetta in Obama’s second-term Cabinet was imminent, a congressional official said.

Obama, who returned to Washington on Sunday from his Hawaiian vacation, was expected to nominate Hagel today. Congress is on break this week.

The officials requested anonymity in order to discuss Hagel’s nomination ahead of Obama.

Hagel, a moderate Republican, built a strong relationship with Obama during their travel as senators. But the former lawmaker has faced withering criticism from Congress since emerging as the front-runner for the Pentagon post.

Hagel is the second-straight Obama favorite for a top national security post to face criticism from Capitol Hill even before being nominated. Rice withdrew her name from consideration for secretary of state amid charges from GOP senators that she misled the public in her initial accounting of the attacks on Americans at a diplomatic post in Benghazi, Libya.

After Rice withdrew, Obama named Sen. John Kerry, D-Mass, to lead the State Department. Kerry is expected to be easily confirmed by his longtime Senate colleagues.

If confirmed, Hagel would take over a Pentagon that faces budget cuts and a scaling back of the U.S.-led war in Afghanistan. Afghan President Hamid Karzai is expected to meet with Obama in Washington this week to discuss the U.S. presence in Afghanistan after the war formally concludes at the end of 2014.

Hagel is likely to support a more rapid withdrawal of U.S. troops from Afghanistan.

Sen. Mitch McConnell, the top Senate Republican, said earlier Sunday that he was reserving judgment on whether to support Hagel. But he predicted the former senator would face serious questions about his stands on Iran and Israel.

Any nominee must have “a full understanding of our close relationship with our Israeli allies, the Iranian threat and the importance of having a robust military,” McConnell said on ABC’s This Week.

Hagel has criticized discussion of a military strike by either the U.S. or Israel against Iran. He also has backed efforts to bring Iran to the table for talks on future peace in Afghanistan. Some lawmakers have been troubled by his comments and actions on Israel, including his reference to the “Jewish lobby” in the United States.

Sen. Lindsey Graham, RS.C., said Sunday that he personally liked Hagel, but that he was “out of the mainstream of thinking on most issues regarding foreign policy.”

“This is an in-your-face nomination of the president to all of us who are supportive of Israel,” Graham said on CNN. “I don’t know what his management experience is regarding the Pentagon - little if any - so I think it’s an extremely controversial choice.”

Those sentiments were echoed by Sen. Ted Cruz, R-Texas, who said Obama was being overly dismissive of criticism about Hagel.

“I think this is a president right now who has drunk the tea,” Cruz said on Fox News Sunday. “He is feeling very good about himself; he is feeling like there can be no opposition to his position. And so, it doesn’t seem - he doesn’t seem terribly concerned that there’s not a lot of support for Chuck Hagel in the Senate.”

Cruz said he would probably vote against Hagel’s confirmation.

McConnell, R-Ky., said Hagel, who left the Senate in 2009, has “certainly been outspoken in foreign policy and defense over the years. The question we will be answering, if he’s the nominee, is do his views make sense for that particular job?”

McConnell said he would “wait and see how the hearings go and see whether Chuck’s views square with the job he would be nominated to do.” He added, “I’m going to take a look at all the things that Chuck has said over the years and review that, and in terms of his qualifications to lead our nation’s military.”

The second-ranking Senate Republican, John Cornyn of Texas, said in a statement that making Hagel defense secretary would be “the worst possible message we could send to our friend Israel and the rest of our allies in the Middle East.” Cornyn did not say he would try to block a Hagel nomination.

The criticism of Hagel has drawn a counterattack from a bipartisan group of former U.S. national security advisers - James Jones, Brent Scowcroft, Zbigniew Brzezinski and Frank Carlucci.

“Hagel is a man of unshakable integrity and wisdom who has served his country in the most distinguished manner in peace and war,” they wrote in a letter published in The Washington Post last month.

Speaking on This Week, Sen. Heidi Heitkamp, the newly elected Democratic senator from North Dakota, also criticized the rancor surrounding Hagel’s nomination, calling it symptomatic of Washington gridlock.

“This kind of fight is the fight that the people of this country get so frustrated about and with,” Heitkamp said. “Let Chuck Hagel get nominated, if he’s going to be nominated, and let’s hear what the senator has to say.”

Hagel’s candidacy has also raised questions among some liberal groups because of a statement he made 14 years ago about President Bill Clinton’s nominee for ambassador to Luxembourg, James Hormel. Hormel, he said, was not qualified because he was “openly, aggressively gay.” Hagel has since apologized.

Obama, in an interview that aired last week on NBC’s Meet the Press, called Hagel “a patriot” who “has done extraordinary work” in the Senate and on an intelligence advisory board, saying nothing in his record would prevent him from serving as defense secretary. He spent 12 years in the Senate, retiring in 2009 after serving on the Foreign Relations Committee. As senator, he called for trimming the defense budgets and often expressed skepticism about involving U.S. troops in extended missions abroad, particularly without international support.

Though he voted for the resolution allowing President George W. Bush to take military action in Iraq, he was among the most outspoken Republican critics of the war. In 2004, he declared that he had “no confidence” in Defense Secretary Donald Rumsfeld’s leadership, and he later joined Democrats in opposing Bush’s plan to send more troops to Iraq.

Illinois Sen. Dick Durbin, the second-ranking Senate Democrat, said on CNN’s State of the Union that Hagel “is a serious candidate if the president chooses to name him.” Information for this article was contributed by Robert Burns, Julie Pace, Jack Gillum and Donna Cassata of The Associated Press; by Michael Schwirtz of The New York Times; and by Hans Nichols and Mark Drajem of Bloomberg News.

Front Section, Pages 1 on 01/07/2013