“I am pleased to announce that I will appoint Robert O'Brien, who is currently very successfully working as the President’s special envoy for hostages in the Department of State, as our new national security adviser,” he wrote on Twitter.

As the president pointed out, he worked a lot with O'Brien for a long time.

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!

- Donald J. Trump (@realDonaldTrump) September 18, 2019

Earlier, The Washington Post wrote that Trump is considering the candidacy of the US special representative for hostages O'Brien for the corresponding post.

On September 10, Trump fired John Bolton from this post. He explained his decision by the fact that he did not agree with many of his proposals.

As the US president noted, Bolton made very big mistakes.