President Obama will on Monday name former Sen. Chuck Hagel to be his next defense secretary, an administration official confirmed to NPR.

The former Republican senator from Nebraska is a Vietnam veteran. He would succeed Leon Panetta, who is retiring.

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Republican senators say former Sen. Chuck Hagel can expect a tough nominating process if President Obama names him to be the next defense secretary.

"I'm going to take a look at all the things that Chuck has said over the years and review that," Senate Minority Leader Mitch McConnell said Sunday on ABC's This Week.

As NPR's Tom Bowman reported last week, Hagel would be the first former enlisted soldier to run the Pentagon. He would succeed Leon Panetta.

According to The Washington Post and other news organizations, Obama will nominate Hagel on Monday. The former Republican senator's past comments on Iran, Israel and gays have come under scrutiny.

Here's more from The Associated Press:

"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."

McConnell said any defense 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."

The comments were echoed by Sen. Lindsey Graham, R-S.C.

"This is an in-your-face nomination by the president to all of us who are supportive of Israel," Graham said on CNN's State of the Union. "I don't know what his management experience is regarding the Pentagon — little, if any, so I think it's an incredibly controversial choice."

But speaking on the same program, Sen. Dick Durbin, the No. 2 Democrat in the Senate, called Hagel "a serious candidate if the president chooses to name him."

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