WASHINGTON • President Donald Trump said yesterday he is naming hostage negotiator Robert O'Brien as his new national security adviser.

"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 Adviser," Mr Trump tweeted.

"I have worked long and hard with Robert. He will do a great job!"

Mr Trump announced that Mr O'Brien will become his fourth national security adviser a week after he ousted Mr John Bolton, citing policy disagreements. Mr O'Brien was among five candidates the Republican President had said on Tuesday were being considered for the post.

As the special 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.

Earlier this year, Mr Trump dispatched Mr O'Brien to Sweden to keep tabs on the criminal case there against rapper A$AP Rocky, who a judge and jury ultimately found guilty of assault last month, several weeks after a street brawl in Stockholm that attracted Mr Trump's attention.

Mr Trump had tried to intervene in the case by offering to personally guarantee bail for the rapper.

Before being named hostage envoy, Mr O'Brien had been a partner at a California law firm and advised the 2016 presidential campaigns of Texas Senator Ted Cruz and former Wisconsin governor Scott Walker.

Previously, he worked for Mr Bolton when he was United Nations ambassador in the George W. Bush administration.

ASSOCIATED PRESS, BLOOMBERG