Sen. Angus King (I-ME) on Tuesday said that if President Donald Trump asked James Comey to drop the FBI’s investigation into former national security adviser Michael Flynn, then it raises the possibility that Trump will be subject to impeachment proceedings.

“If indeed the President tried to tell the director of the FBI who worked for him that he should drop an investigation, whether it was Michael Flynn or whether it was some investigation that had nothing to do with Russia or politics or the election, that’s a very serious matter,” King said on CNN.

“If these allegations, Senator, are true, are we getting closer to the possibility of yet another impeachment process?” Wolf Blitzer asked.

“Reluctantly, Wolf, I have to say yes, simply because obstruction of justice is such a serious offense,” King said.

He said it “was in fact one of the offenses that was listed in the last two impeachments that have gone on” in Congress.

“I think we have to be a little bit cautious. This is of immense importance,” King said. “It’s one of the most important things that I’ve been involved with in my political life.”

He cited the White House’s denials that Trump asked Comey to end the probe and Trump’s suggestion that he recorded conversations with the former FBI head.

“We’re going to have to hear from Director Comey,” King said. “And also, if the White House has been saying all day that this never happened, then I think they should come forth with whatever evidence that they have, whether it’s tapes or notes made by someone at the White House to contradict this.”

The New York Times reported on Tuesday that Trump asked Comey to shut down his bureau’s investigation into Flynn, a request that Comey documented in a memo. That report was quickly corroborated by NBC News, CNN and the Washington Post.