The concerns about Hagel complicate his path to Senate confirmation but are not necessarily calamitous as the White House pushes for the first Vietnam War veteran to oversee a military emerging from two wars and staring at deep budget cuts.
Obama also tapped White House counterterrorism adviser John Brennan to head the CIA. Brennan, a 25-year CIA veteran, faces no major obstacles, but he is expected to be hit with questions about torture and administration leaks of secret information.
Moments after Obama announced his selection of Hagel and called him "the leader that our troops deserve," some Senate Republicans voiced opposition to the former Nebraska lawmaker who spent 12 years in the Senate.
"Given Chuck Hagel's statements and actions on a nuclear Iran, Hamas and Hezbollah, I think his confirmation would send exactly the wrong message to our allies and enemies alike," Sen. David Vitter, R-La., said in a statement. "Israel, our strongest ally in the region, is dealing with a lot of threat and uncertainty right now; Hagel would make that even worse."
Other Senate Republicans, including the No. 2 GOP lawmaker, John Cornyn of Texas, new member Ted Cruz of Texas and Mississippi's Roger Wicker, signaled they would vote against the nomination.
Hagel has upset some Israel backers with his comment about the "Jewish lobby," his votes against unilateral sanctions against Iran while backing international penalties on the regime in Tehran and his criticism of talk of a military strike by either the U.S. or Israel against Iran.
He also upset gay rights groups over past comments, including his opposition in 1998 to President Bill Clinton's choice of James Hormel as ambassador to Luxembourg. He referred to Hormel as "openly, aggressively gay." Hagel recently apologized, saying his comments were "insensitive."
Those remarks and actions have created fierce opposition from some pro-Israel groups, criticism from some Republicans and unease among some congressional Democrats.
The Log Cabin Republicans took out a full-page ad in The Washington Post highlighting their opposition to Hagel, and Gregory T. Angelo, interim executive director of the gay rights group, said the gay and lesbian grassroots organization is considering other steps in a campaign against Hagel's nomination.
House Majority Leader Eric Cantor, R-Va., who does not have a vote on the nomination, called Hagel the "wrong man" for the job and complained that "his inflammatory statements about Israel are well outside the mainstream."
In an interview with the Lincoln (Neb.) Journal Star, Hagel said his statements have been distorted and there is "not one shred of evidence that I'm anti-Israeli, not one (Senate) vote that matters that hurt Israel."
In a critical sign of support for Hagel's prospects, the 66-year-old moderate Republican attracted words of praise from Senate Majority Leader Harry Reid, D-Nev., Senate Armed Services Committee Chairman Carl Levin, D-Mich., and Sen. Dianne Feinstein, D-Calif., who heads the Intelligence panel.