WASHINGTON, Jan. 7 (Xinhua) -- U.S. President Barack Obama on Monday announced that he will nominate former Republican senator Chuck Hagel as the next defense secretary, and his counterterrorism adviser John Brennan to lead the Central Intelligence Agency (CIA).

　　At a formal announcement event at the White House, Obama called Hagel "the leader our troops deserve," and urged the Senate to move quickly on the confirmation process.

　　"As I saw during our visits together to Afghanistan and Iraq, the troops see a decorated combat veteran of character and strength," said the president, stressing that Hagel "knows that war is not an abstraction."

　　Sitting Defense Secretary Leon Panetta also commended Obama's choices at the event, saying that Hagel has a "deep understanding of national security issues."

　　Hagel, 66, a decorated Vietnam War veteran and a moderate Republican, is expected to be a trusted ally of Obama on the issue of exit from Afghanistan. He served for two terms from 1997 to 2009 as U.S. senator for Nebraska, and was a leading Republican critic of the Iraq War. He is now chairperson for the President's Intelligence Advisory Board and a professor at Georgetown University.

　　In his brief comments on the nomination, Hagel said that he was grateful for the opportunity to serve the troops and to help " strengthen our country and our country's alliances."

　　His possible nomination has been rumored for weeks and sparked criticism. Republican lawmakers have already stood in line to voice their opposition to Obama's selection of Hagel, raising questions over whether the former senator would be a strong ally of Israel and be tough enough on Iran.

　　U.S. House Majority Leader Eric Cantor issued a statement on Monday, calling Hagel "the wrong man for the job at such a pivotal time."

　　Hagel and Brennan, along with veteran Democratic Senator John Kerry, Obama's nominee for secretary of state announced last month, would form the centerpiece of the president's second-term national security team.

　　But unlike Kerry who has won bipartisan support, the nominations for Hagel and Brennan could face controversy and even a confirmation fight at the Capitol Hill.

　　Brennan, a 25-year CIA veteran, withdrew from consideration for the CIA's top position in 2008 amid questions about his alleged connection to harsh interrogation techniques used during the George W. Bush administration.

　　If confirmed by the Senate, Brennan would succeed retired General David Petraeus, who resigned abruptly days after Obama won the re-election due to a scandal over his extramarital affair with his biographer.