WASHINGTON – President Obama is expected to nominate Chuck Hagel, a former Republican senator and Vietnam veteran, to be defense secretary, officials said, setting up a confirmation battle with lawmakers and interest groups critical of his views on Israel and Iran.

White House officials said Friday that the president had not formally offered the job to Hagel, but others familiar with the process said that the announcement could come as soon as Monday.

Hagel, who was elected to the Senate from Nebraska in 1996 and retired in 2008, was awarded two Purple Hearts for wounds he received as a soldier in Vietnam.

His experience serving in that war made him wary about using force unless other options have been tried, he said in a recent interview with the history magazine “Vietnam.”

“I’m not a pacifist. I believe in using force but only after a very careful decision-making process. I will do everything I can to avoid needless, senseless war,” he said.

By nominating a Republican to run the Defense Department, Obama would give his second-term national security team a bipartisan cast as the White House is rapidly winding down the war in Afghanistan and planning for even deeper cuts in the defense budget.

Hagel’s criticism of the Iraq war has made him deeply unpopular with many conservative Republicans, however.

The choice also sets up a possibly contentious confirmation fight with Israel’s defenders in Washington, some of whom mounted a public campaign to head off his nomination.

They criticized Hagel for past comments calling on Israel to negotiate with Palestinian groups and for opposing some sanctions aimed at Iran.

Hagel, who would replace Leon Panetta as defense secretary, has also been criticized by some liberal Democrats and gay rights organizations for a comment he made during Bill Clinton’s presidency, calling an ambassadorial nominee “openly, aggressively gay” — a comment Hagel recently apologized for.

Diving into a fight over nominating Hagel would appear to mark a sharp departure for Obama, who has generally avoided battles over selections for major posts.

But a decision to pick another candidate would also have been damaging to Obama, because it would have been his second surrender on a top Cabinet choice within a month.

Susan Rice, the U.S. ambassador to the United Nations, withdrew her name from consideration as a possible secretary of state nominee last month after drawing heavy criticism from Republicans over her statements after the September attacks on a U.S. diplomatic mission in Benghazi, Libya.

The selection of Hagel would also leave unresolved the problem of how Obama is going to add more women to the senior ranks of his national security apparatus.

Senior Democratic women — including some in the administration — have noted that aside from Secretary of State Hillary Rodham Clinton, foreign policy has been decided by a small group of men in the White House.

Though senators from both parties have voiced reservations about Hagel, few have announced they would vote against him, a caution the White House may be counting on to get him confirmed.

Hagel’s record on Israel and Iran are likely to be the main focus of the nomination battle. William Kristol, the editor of the conservative Weekly Standard, published a “special editorial” Friday accusing him of having “dangerous views on Iran” and an “unpleasant distaste for Israel and Jews.”

Critics have pointed to a comment Hagel made in 2008 to author and former State Department Middle East peace negotiator Aaron David Miller about why he sometimes opposed pro-Israel groups in the Senate.

“The Jewish lobby intimidates a lot of people up here,” Hagel said, but “I’m a United States senator. I’m not an Israeli senator.”

They also have cited his calls for direct negotiations with Hamas, the Palestinian militant group that the U.S. and Israel refuse to deal with directly.

But defenders and former aides say Hagel showed his support for Israel by voting repeatedly to provide it with military aid and by calling for a comprehensive peace deal with the Palestinians that should not include any compromise regarding Israel’s Jewish identity and that leaves Israel “free to live in peace and security.”

Obama and Hagel formed a close relationship in the Senate, and their foreign policy views seem closely aligned.