President Donald Trump‘s former attorney, Michael Cohen, claims that the then-candidate Trump knew in advance of a June 6, 2016 Trump Tower meeting, involving Trump’s son, top campaign officials and a Russian lawyer, CNN reported.

Although, Cohen has no evidence to offer that corroborates has claim, but says he is willing to make that assertion to special counsel Robert Mueller, a source with knowledge of Cohen’s account said.

Donald Trump Jr., Trump son-in-law Jared Kushner, and former Trump campaign chairman Paul Manafort met with Russian attorney Natalia Veselnitskaya in the Trump Tower, a gathering arranged by Trump Jr. because he believed Veselnitskaya had damaging information about Hillary Clinton.

Trump denied knowledge of the meeting in a tweet Friday morning, blaming Cohen with his reported financial troubles.

An FBI raid on Cohen’s office in April sought information about taxi owners who had financial dealings with Cohen, CNN reported.

Rudy Giuliani, the President’s attorney, told CNN that Cohen has “been lying all week, he’s been lying for years.”

“He’s been lying for years,” Giuliani said. “I mean, the tapes that we have demonstrate any number of very serious lies by him back a year and a half ago, including his fooling people, hiding tape recordings, telling them they weren’t recorded, lying to their face, breaking faith with them, taping his client, which is a disbarable offense. I don’t see how he has any credibility.”

“The significance of this report will depend on the facts,” said Barbara McQuade, a former U.S. attorney from eastern Michigan, told Politico. “If Trump was aware of the meeting in advance and encouraged it to go forward, then he could face criminal exposure under a number of different theories.”

“He could be in violation of campaign finance laws for accepting a thing of value from a foreign national in relation to an election” she continued. “If he knew that the source of the information was from illegal hacking, he could be charged with accessory after the fact to a violation of the Computer Fraud and Abuse Act. He could also be charged with conspiracy to defraud the United States by impeding the fair administration of elections. In addition, he could be charged with obstruction of justice for misdirecting investigators by dictating a misleading press release.”