President Donald Trump on Friday continued the White House’s stonewalling on when exactly he knew former national security adviser Michael Flynn lied to the FBI about his contacts with former Russian ambassador Sergey Kislyak.

“When did you find out Michael Flynn lied to the FBI? When did you find out?” an inquiring reporter asked, as Trump answered questions before boarding Marine One on his way to deliver a speech at the FBI National Academy graduation.

“What else is there?” he asked, sounding exasperated.

“You know the answer,” he said. “How many times has that question been asked?”

But journalists don’t know the answer; the White House has repeatedly refused to answer the question.

Flynn was fired, the White House said at the time, for lying to the vice president about his discussions of sanctions with Kislyak before the current administration took office. But after he pleaded guilty this month as part of special counsel Robert Mueller’s probe to lying to the FBI about those conversations, Trump said in a tweet that he’d known that Flynn lied to the FBI — a new claim which further opened the President up to accusations of obstructing justice. Trump’s lawyer, John Dowd, later claimed to have written the tweet:

I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide! — Donald J. Trump (@realDonaldTrump) December 2, 2017

Reporters have repeatedly asked White House press secretary Sarah Huckabee Sanders about when Trump first knew Flynn had lied to the FBI. She’s directed those questions to Trump’s personal lawyers, who haven’t offered any answers, except when Dowd told Axios: “the tweet did not admit obstruction,” and that the President “cannot be guilty of obstruction of justice.”

Trump also told reporters Friday that “it’s a shame what’s happened to the FBI, but we’re going to rebuild the FBI.”

“There is absolutely no collusion, that has been proven,” he said, criticizing the cost of the investigations of Russian meddling in the 2016 election. “I didn’t make a phone call to Russia, I have nothing to do with Russia.”