Listen Live

 (CNN) — President Donald Trump named Robert O’Brien, a U.S. hostage negotiator, his new national security adviser on Wednesday.

“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. I have worked long & hard with Robert. He will do a great job!” Trump tweeted.

The announcement came a week after Trump fired John Bolton, citing disagreements on several issues, and as he confronts a major foreign policy crisis following the attack on Saudi oil facilities — which the administration has blamed on Iran.

Aides expected an announcement because acting national security adviser Charlie Kupperman, who took over in Bolton’s absence, was not scheduled to travel to New York for next week’s meeting of the United Nations General Assembly.

Trump personally dispatched O’Brien to help free US rapper A$AP Rocky from Swedish prison earlier this year.

The hostage negotiator interviewed for the post with the President and acting chief of staff Mick Mulvaney last week and enjoyed support from Secretary of State Mike Pompeo, who is now the most influential national security voice in the administration.

Trump, who is known to respond well to flattery, has recounted praise from O’Brien in tweets and in conversations, suggesting that the new national security adviser also knows how to handle the President and his mercurial moods.

O’Brien has also made Trump look good — giving him numbers to boast about and successes that made for high profile media coverage.

Speaking to reporters aboard Air Force One on Tuesday, Trump again highlighted O’Brien’s praise of him in securing the release of hostages.

“Robert O’Brien said, ‘Trump is the greatest hostage negotiator in history.’ He happens to be right,” Trump said, according to pool reporters. “We are 38-0. 38-0, ask Robert. In fact, I had never heard the term. Robert O’Brien said Donald Trump is the greatest hostage negotiator of all time. 38-0. At the time he said it we were 29-0. We are 38-0.”

CNN has contacted the State Department for further details on the numbers cited by Trump.

During an Oval Office meeting in March, O’Brien celebrated Trump for his success returning American hostages.

“This wouldn’t happen with all of these hostages and detainees without the support of the President,” he said. “The President has had unparalleled success in bringing Americans home without paying concessions.”

Trump was considering a number of other candidates for the post, and yesterday named five people under consideration: O’Brien, Ricky Waddell, Fred Fleitz, Keith Kellogg, and Lisa Gordon-Hagerty.

(Photo by Olivier Douliery/Getty/AFP.)