Critics said the decorated Vietnam combat veteran is a "radical" unqualified to lead the U.S. military. A top White House official expressed "grave concern" over the delayed confirmation vote, adding that there was nothing to worry about in any disclosures that may yet come.
"No, I don't believe he's qualified," Sen. John McCain, R-Ariz., said of his fellow Republican and former Senate colleague. "But I don't believe that we should hold up his nomination any further, because I think it's (been) a reasonable amount of time to have questions answered."
McCain and other Republicans have angered President Barack Obama by delaying him from rounding out his second-term national security team, which includes Hagel and John Brennan, the White House counterterrorism adviser who is awaiting confirmation to become CIA director. Former Massachusetts Sen. John Kerry assumed his post as secretary of state at the beginning of February.
Critics contend that Hagel, who snubbed McCain by staying neutral in the 2008 presidential race between McCain and Obama, isn't supportive enough of U.S. ally Israel and is unreasonably sympathetic to Iran, which has defied international pressure to halt its pursuit of material that could be used to make nuclear weapons.
Hagel's nomination also became ensnared in Republican lawmakers' questioning of how the White House handled the Sept. 11 attack against a U.S. diplomatic mission in Benghazi, Libya, in which the U.S. ambassador and three other Americans were killed. Hagel was not involved in the administration's response.
GOP senators also have challenged Hagel's past statements and votes on nuclear weapons, and his criticism of President George W. Bush's administration.
Republicans last week delayed a confirmation vote, but have indicated that one will be allowed when senators return from a break on Feb. 25.
Sen. Lindsey Graham, R-S.C., another leader of the opposition to Hagel, referred to a letter he received from Hagel in response to questions about past statements on Israel. Graham said that, as a result, he'll take Hagel "at his word, unless something new comes along."
Still, the weeklong delay buys Hagel's opponents even more time to rally additional opposition.
White House chief of staff Denis McDonough, making his first appearances on the Sunday talk shows in his new role, was asked if the delays in filling out Obama's Cabinet presented a threat to national security.
"It's a grave concern," he said.
Hagel "has one thing in mind: how do we protect the country," McDonough said, adding that there was nothing to worry about in any disclosures about Hagel that may still come.
Graham said senators were taking seriously their responsibility to scrutinize "one of the most unqualified, radical choices for secretary of defense in a very long time."
Last week, Obama criticized Republican senators for delaying the nomination, accusing them of playing politics with national security.
"It's just unfortunate that this kind of politics intrudes at a time when I'm still presiding over a war in Afghanistan and I need a secretary of defense who is coordinating with our allies to make sure that our troops are getting the kind of strategy and mission that they deserve," he said during a Google-sponsored online forum.
McDonough appeared on ABC's "This Week," while McCain spoke on NBC's "Meet the Press" and Graham was interviewed by "Fox News Sunday."