WASHINGTON, DC - FEBRUARY 01: National Security Adviser Michael Flynn answers questions in the briefing room of the White House February 1, 2017 in Washington, DC. Flynn said the White House is "officially putting Iran on notice" for a recent missile test and support for Houthi rebels in Yemen. (Photo by Win McNamee/Getty Images)

WASHINGTON (CBS.com/AP) — Embattled National Security Adviser Michael Flynn resigned Monday following reports that he discussed U.S. sanctions with a Russian envoy prior to President Donald Trump’s inauguration.

In a statement obtained by CBS News Monday evening, Flynn wrote:

“I inadvertently briefed [VP Pence] and others with incomplete information regarding my phone calls with the Russian Ambassador.”

Flynn: "I inadvertently briefed [VP Pence] and others with incomplete information regarding my phone calls with the Russian Ambassador." pic.twitter.com/NnnnBsvhHc — CBS News (@CBSNews) February 14, 2017

Lt. General Joseph Kellogg, Jr. has been named acting national security adviser, CBS News reported.

On Friday, The Washington Post reported that Flynn addressed sanctions against Russia in a call with Kislyak. The report contradicted repeated denials from Trump officials, including Pence, who vouched for Flynn in a televised interview.

Flynn has since told administration officials that sanctions may have come up in the calls, which coincided with the Obama administration slapping penalties on Russia for election-related hacking.

New Jersey Gov. Chris Christie, who led Trump’s transition planning before the election, said Flynn would have to explain his conflicting statements about his conversations with Kislyak to Trump and Pence.

“Gen. Flynn has said up to this point that he had not said anything like that to the Russian ambassador. I think now he’s saying that he doesn’t remember whether he did or not,” Christie said on CNN. “So, that’s a conversation he is going to need to have with the president and the vice president to clear that up, so that the White House can make sure that they are completely accurate about what went on.”

The controversy surrounding Flynn comes as the young administration grapples with a series of national security challenges, including North Korea’s reported ballistic missile launch. The president, who was joined at his Mar-a-Lago estate by Japanese Prime Minister Shinzo Abe, voiced solidarity with Japan.

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