Donald Trump has named Robert O’Brien, his chief hostage negotiator and an established figure in Republican policy circles, as his new national security adviser.

Mr O’Brien, the fourth person in two years to hold the job, becomes the administration’s leader on national security amid rising tensions with Iran following the weekend attack on Saudi oil installations and fresh uncertainty in Afghanistan after the halt in peace talks with the Taliban.

The announcement came a week after the president ousted John Bolton from the post, citing policy disagreements.

Mr O’Brien, who made headlines in July when he was dispatched to Sweden to monitor the assault trial of American rapper ASAP Rocky, was among five candidates Mr Trump said were under consideration.

Robert O’Brien
Robert O’Brien (Erik Simander/TT/AP)

“I am pleased to announce that I will name Robert C. O’Brien, currently serving as the very successful Special Presidential Envoy for Hostage Affairs at the State Department, as our new National Security Advisor,” Trump tweeted. “I have worked long & hard with Robert. He will do a great job!”

Mr Trump abruptly forced Mr Bolton out on September 10 after he and his hawkish national security adviser found themselves in strong disagreement over the administration’s approach to Iran, Afghanistan and a host of other global challenges.

As the presidential envoy for hostage affairs at the State Department, Mr O’Brien worked closely with the families of American hostages and advised administration officials on hostage issues. He helped secure the release in February of Danny Burch, who was freed after 18 months in captivity.

He has also worked on the case of missing US journalist Austin Tice, who was captured in Syria in 2012. Mr O’Brien has said he is confident Mr Tice is still alive though it is unclear who is holding him.

The White House sent Mr O’Brien to Sweden to monitor the case of ASAP Rocky, who was charged with assault. The rapper, whose real name is Rakim Mayers, was permitted to return to Los Angeles to await the verdict of a Swedish court that found him guilty in a street brawl.

Mr O’Brien previously helped lead the department’s public-private partnership for justice reform in Afghanistan during the Bush and Obama administrations.

From 2008 to 2011, Mr O’Brien was a presidentially appointed member of a government committee that advises on issues related to the trafficking of antiquities and other cultural items.

In 2005, George W Bush nominated him to be US representative to the UN General Assembly, where he worked with Mr Bolton. Mr O’Brien was confirmed by the Senate.

He also was an adviser on the Republican presidential campaigns of former Wisconsin governor Scott Walker, ex-Massachusetts governor Mitt Romney and Texas senator Ted Cruz.

Earlier in his career, he was a senior legal officer for the UN Security Council commission that decided claims against Iraq that arose from the Gulf War. He was a major in the US Army Reserve.

Mr O’Brien has a law degree from the University of California, Berkeley, and co-founded a law firm in Los Angeles focused on litigation and international arbitration issues.

He is the author of While America Slept, a collection of essays on US national security and foreign policy billed as a “wake-up call to the American people”.