United States President Donald Trump’s National Security Adviser Michael Flynn resigned on Monday after reports emerged that he had discussed the country’s sanctions with Russia. “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.

Flynn had told Vice President Mike Pence that he had not discussed lifting US sanctions with Russia. However, later it was found that the matter had, in fact, cropped up in conversation.

Flynn’s resignation came hours after Trump said he was in talks with Pence to review the situation, reported Reuters. Former acting attorney general Sally Q Yates, who was fired for opposing Trump’s ban order on immigrants from seven Muslim-majority countries, had earlier warned the White House that Flynn could be vulnerable to Russian blackmail.

Retired general and Chief of Staff of the White House National Security Council Keith Kellogg has been named the acting national security adviser. Among the many names doing the rounds for the post, a White House official told Reuters that retired general and former CIA director David Petraeus was a front-runner. Apart from Petraeus, Vice Admiral Bob Harward and Kellogg are also being considered for the post, reported CNBC.