WASHINGTON (AP) -- The Senate's Republican leader said Sunday he is reserving judgment on whether to support former Sen. Chuck Hagel, the front-runner to be the next defense secretary, and predicted that his former colleague would face serious question about his stands on Iran and Israel.

President Barack Obama may round out his new national security leadership team this coming week, with a nomination for Pentagon chief expected and a pick to lead the Central Intelligence Agency possible. Obama was returning Sunday from his vacation in Hawaii.

Sen. Mitch McConnell, R-Ky., 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."

McConnell told ABC's "This Week" that Hagel, a Nebraska Republican 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."

Obama, in an interview that aired last Sunday on NBC's "Meet the Press" called Hagel "a patriot" who "has done extraordinary work" in the Senate and on an intelligence advisory board.

Illinois Sen. Dick Durbin, the second-ranking Senate Democrat, told CNN's "State of the Union" that Hagel "is a serious candidate if the president chooses to name him."

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.

Obama has nominated Sen. John Kerry, D-Mass., as his next secretary of state, in what was the president's first step in filling out his second term Cabinet and national security team.

Kerry, as well as the nominees for the Pentagon and CIA, must be confirmed by the Senate.