President Donald Trump tweeted support early Friday for Michael Flynn following a report Thursday night that the disgraced former national security adviser, who resigned after mischaracterizing interactions with Russian officials, has offered to testify to the FBI and Congress in exchange for immunity.

"Mike Flynn should ask for immunity," the president wrote, "in that this is a witch hunt (excuse for big election loss), by media & Dems, of historic proportion!"

The Wall Street Journal first reported Flynn's offer to the FBI and the Senate and House intelligence committees, all of which are investigating his and other Trump team officials' alleged ties to the Russian government, based on an anonymous source familiar with the discussions. Flynn's lawyer, Robert Kelner, wouldn't confirm the offer to the Journal, but said the former Defense Intelligence Agency chief and Trump campaign aide "certainly has a story to tell, and he very much wants to tell it, should the circumstances permit."

At a press conference Friday afternoon, White House spokesman Sean Spicer said Trump's tweet calls for transparency and openness.

Trump's tweet means, "Do whatever you have to do to go up," and testify before Congress, Spicer said.

"That's quite the opposite of what you would normally think [about] somebody not trying to get to the bottom of something," he said.

The fact that Flynn, 58, requested immunity suggests he fears legal reprisal for discussing his three-week tenure as national security adviser and potential ties to the Russia – accusations that have dogged the Trump campaign and now the president's administration. Flynn himself said in September while advising the Trump campaign that receiving immunity "means you have probably committed a crime," then referencing statements by Hillary Clinton campaign chairman John Podesta. Trump also said while on the campaign trail in September that accepting legal immunity implies guilt.

Trump accepted Flynn's resignation in February, 25 days into the administration, after it was reported Flynn had mischaracterized to Vice President Mike Pence the nature of phone conversations Flynn had with Russian ambassador Sergey Kislyak between election day and the inauguration. It is common for senior White House officials, particularly those dealing with foreign affairs or national security, to reach out to officials from foreign governments.

Flynn, a career military officer who retired in 2014 as a lieutenant general, had also received tens of thousands of dollars in speakers fees from Russian companies, including state-owned television service RT, shortly after beginning work with the Trump campaign.

In February Flynn filed registration forms demonstrating he worked as a foreign agent to lobby for Turkish interests in Washington.