Trump's national security aide Flynn resigns over Russian contacts

President Donald Trump's national security adviser, Michael Flynn, resigned late on Monday after revelations that he had discussed US sanctions on Russia with the Russian ambassador to the United States before Trump took office and misled Vice President Mike Pence about the conversations.

The White House issued a statement just after 11pm in Washington announcing the resignation hours after it was reported that the Justice Department had warned the White House weeks ago that Flynn could be vulnerable to blackmail for contacts with Russian ambassador Sergey Kislyak before Trump took power on 20 January.

Flynn had promised Pence he had not discussed US sanctions with the Russians, but transcripts of intercepted communications, described by US officials, showed that the subject had come up in conversations between him and the Russian ambassador.

Such contacts could potentially be in violation of a law banning private citizens from engaging in foreign policy, known as the Logan Act.

Pence had defended Flynn in television interviews and was described by administration officials as upset about being misled.

The White House statement also named retired army general Joseph Keith Kellogg as acting national security adviser, pending the appointment of a permanent successor. It was reported that a third general, former CIA director David Petraeus, was due to meet Trump on Tuesday.

In his resignation letter, Flynn claimed he had mistakenly misled Pence and other Trump officials about the nature of phone calls in December to the Russian ambassador, Sergey Kislyak.

"Unfortunately, because of the fast pace of events, I inadvertently briefed the Vice President-elect and others with incomplete information regarding my phone calls with the Russian ambassador. I have sincerely apologised to the President and the Vice President, and they have accepted my apology," Flynn said in his resignation letter.

When intelligence leaks about the communications began appearing last month, Pence and other White House officials insisted the contact had involved only an exchange of Christmas greetings and arrangements for a future phone conversation between Trump and Vladimir Putin.

Flynn submitted his resignation hours after Trump, through a spokesman, pointedly declined to publicly back Flynn, saying he was reviewing the situation and talking to Pence.

A US official confirmed a Washington Post report that Sally Yates, the then-acting US attorney general, told the White House late last month that she believed Flynn had misled them about the nature of his communications with the Russian ambassador. She said Flynn might have put himself in a compromising position, possibly leaving himself vulnerable to blackmail, the official said. Yates was later fired for opposing Trump's temporary entry ban for people from seven mostly Muslim nations.

Flynn’s departure could slow Trump's bid to warm up relations with Russian President Vladimir Putin.