National security adviser Michael Flynn abruptly resigned late Monday after acknowledging “he had become a lightning rod” over his dealings with Russia, White House counselor Kellyanne Conway said Tuesday.

Flynn’s departure comes after he misled Vice President Mike Pence and other senior White House officials about information he shared with the Russian ambassador to the United States.

“In the end, it was misleading the vice president that made the situation unsustainable,” Conway told TODAY’s Matt Lauer.

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“The incomplete information or the inability to completely recall what did or did not happen as reflected in his debriefing of particular phone calls — that really is what happened here,” she said.

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Flynn’s departure comes less than a month into the job and follows revelations about information he shared with Russian Ambassador Sergey Kislyak over American sanctions against Russia in late December, weeks before Trump took office.

"He knew he had become a lightening rod and he made that decision," Conway said.

NBC NEWS: Flynn quits as national security adviser over talks with Russia

Flynn initially told the the vice president he did not discuss sanctions imposed on Russia, a claim Pence repeatedly widely during media interviews. In his resignation letter, Flynn addressed the issue.

"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 apologized to the President and the Vice President, and they have accepted my apology," Flynn wrote in the letter.

On TODAY, Conway was asked repeatedly why, despite reports that the Justice Department told the White House last month that Flynn had misled them and even put himself at risk for blackmail, he continued to retain the president's full trust.

“That’s one characterization," Conway said. "But the fact is that General Flynn continued in that position and was in the presidential daily briefings, was part of the leader calls as recently as (Monday) … and as time wore on, obviously the situation had become unsustainable.”

Conway added that the president accepted Flynn's resignation and "wishes him well, and we're moving on," noting three "very strong candidates" the administration is considering to replace him.