US President Barack Obama has announced his choice of Chuck Hagel as his next defence secretary and counter-terrorism adviser John Brennan to lead the Central Intelligence Agency, two potentially controversial picks for his second-term national security team.
Hagel has faced tough criticism from congressional Republicans who say the former Republican senator is anti-Israel and soft on Iran.
Brennan, a 25-year CIA veteran, withdrew from consideration for the spy agency's top job in 2008 amid questions about his connection to criticised interrogation techniques during the George W Bush administration.
Brennan's nomination also will draw attention to the secretive US drone program, which is unpopular overseas. He was the first Obama administration official to publicly acknowledge the targeted killing operations.
Obama called Hagel "the leader that our troops deserve" and said on Monday that both men understand "the work of protecting our nation is never done".
Along with secretary of state nominee Senator John Kerry, Hagel and Brennan would play key roles implementing and shaping Obama's national security priorities. All three must be confirmed by the Senate.
In nominating Hagel, Obama signalled he is willing to take on a tough confirmation fight. The 66-year-old moderate Republican has criticised discussion of a military strike by either the US or Israel against Iran. He also irritated some Israel supporters with his reference to the "Jewish lobby" in the United States. And he has backed efforts to bring Iran to the table for future peace talks in Afghanistan.
The second-ranking Senate Republican, John Cornyn, said in a statement that making Hagel defence secretary would be "the worst possible message we could send to our friend Israel and the rest of our allies in the Middle East".
White House officials say Hagel's positions on Israel and Iran have been misrepresented. They cite his Senate votes for billions in military assistance to Israel and his support for multilateral sanctions on Tehran.
Ben Rhodes, Obama's deputy national security adviser, said Hagel will be "completely in line with the president" on both issues.
"The president has a record of unprecedented security co-operation with Israel, and that's going to continue no matter who the defence secretary is," Rhodes said.
Hagel has also been criticised by some Democrats for saying in 1998 that a nominee for an ambassador post was "openly, aggressively gay". He has since apologised for those comments.
Hagel is the second straight Obama favourite for a top national security post to face criticism from lawmakers even before being nominated.
United Nations Ambassador Susan Rice withdrew her name from consideration for secretary of state amid charges from Republican senators that she misled the public in her initial accounting of the deadly attacks on Americans in September at a diplomatic post in Benghazi, Libya.
Both Hagel and Brennan have close relationships with Obama, who values loyalty in his inner circle.
Brennan, as the president's top counter-terrorism adviser, was deeply involved in the planning of the 2011 raid that killed September 11 mastermind Osama bin Laden. And he has led administration efforts to quell the growth of terror organisations in Yemen and elsewhere in the Middle East and North Africa.
If confirmed, Brennan will succeed David Petraeus, who resigned in November after admitting to an affair with his biographer.