U.S. President Trump fires national security adviser John Bolton

President Donald Trump abruptly announced in a tweet Tuesday that he has asked national security adviser John Bolton to resign, noting that he "strongly disagreed with many" of Bolton's suggestions "as did others in the administration," CNN reports.

"I thank John very much for his service. I will be naming a new National Security Advisor next week," Trump wrote.

The tweet came just one hour after the White House press office said Bolton was scheduled to appear at a Tuesday press briefing alongside Secretary of State Mike Pompeo and Treasury Secretary Steve Mnuchin.

Asked during the briefing whether he and Mnuchin were surprised that Bolton was fired, given that he was supposed to appear alongside them, Pompeo said, "I'm never surprised."

Bolton, however, maintains he offered to leave his post voluntarily, tweeting minutes after Trump's announcement, "I offered to resign last night and President Trump said, 'Let's talk about it tomorrow.'"

Bolton reiterated the point that he offered to resign to Fox News Tuesday.

His resignation letter to Trump, dated Tuesday, was short and to the point with Bolton writing: 'I hereby resign, effective immediately, as Assistant to the President for National Security Affairs. Thank you for having afforded me this opportunity to serve our country."

The White House is already discussing potential candidates to replace Bolton, several sources told CNN. There are at least 10 names being circulated and there does not appear to be a shortlist at this time.

Trump said he will make a decision next week but given the President's unpredictable nature, sources warn that he could choose someone who is not under discussion right now.