Washington (CNN) Rudy Giuliani denied Monday that the disclosure by Donald Trump's attorneys that the President dictated a crucial statement on the infamous June 2016 Trump Tower meeting -- a reversal from past denials -- constituted a lie, instead claiming it was a routine mistake.

"It was a mistake," Giulani, a lawyer for Trump in the Russia investigation, said on CNN's "Cuomo Prime Time" Monday. "I swear to God, it was a mistake."

The meeting -- and Trump's role in the statement -- has become a central focus of special counsel Robert Mueller's investigation into Russian meddling in the 2016 election and possible collusion between Russia and the Trump campaign. The President's son, Donald Trump Jr., accepted the meeting, along with several other campaign officials, on the premise that he would receive dirt on Hillary Clinton from the Russian government, though the attendees said such information didn't surface.

The statement, given to The New York Times last summer, said the meeting was primarily about adoption policies, and spokespersons for the President repeatedly denied that Trump was involved in crafting it. But it was revealed over the weekend in a letter from the President's attorneys to Mueller that Trump did in fact "dictate" the statement -- raising the question of why Trump tried to hide the true premise of the meeting.

"I don't think anybody's lying," Giuliani told CNN's Chris Cuomo, as part of an interview in which he also railed against former FBI Director James Comey and dismissed the idea that his role defending Trump would hurt his legacy. "I think a mistake was made."

Read More