Trump’s ‘good luck’ tweet to Flynn shows someone is feeding him secrets from Mueller probe: Legal expert

President Donald Trump wished "good luck" to disgraced national security adviser Michael Flynn -- who will be sentenced Tuesday for lying to FBI agents.

The retired U.S. Army general has pleaded guilty to lying to investigators, and has agreed to cooperate with special counsel Robert Mueller, who said Flynn deserved a light sentence because had provided him with substantial assistance in the Russia probe.

"Good luck today in court to General Michael Flynn," Trump tweeted. "Will be interesting to see what he has to say, despite tremendous pressure being put on him, about Russian Collusion in our great and, obviously, highly successful political campaign. There was no Collusion!"

Former U.S. Attorney Daniel Goldman and other legal experts were astonished by the president's tweet, and they tried to decipher what the president actually meant with the statement.

"No doubt he has been told that Flynn did not provide evidence to the special counsel of a conspiracy with Russia to interfere with the election," Goldman tweeted. "Big question: who told him?"

Lawfare managing editor Quinta Jurecic said the president had again apparently violated the law against witness tampering with his tweet, after a similar one aimed at associate Roger Stone.

National security journalist Marcy Wheeler said the president's tweet could come back to haunt Flynn as he hopes to avoid prison.

"Flynn's got ground to make up on showing remorse," she tweeted. "Now Trump is pressuring him not to."