But on another significant aspect of the investigation - whether the president tried to obstruct the inquiry itself - Mueller and his investigators understood that issues of executive privilege could complicate their pursuit of a presidential interview and did not ask for written responses on that matter, according to the letter, which was sent Friday.
Mueller has reportedly not ruled out an in-person interview with Trump, though the letter did not ask for answers on obstruction of justice questions, leading team Trump to think that a sit-down with Mueller could be much less expansive in scope than they feared.
Trump then suggested that the special counsel personally dislikes him, and claimed Mueller's team of prosecutors had a partisan vendetta against him.
Following the "kissing" comments, the President went off on a familiar diatribe about the supposed illegitimacy of Mueller's investigation, which has already resulted in almost 40 indictments against Trump associates and Russians.
Mueller's office had previously indicated that it had many questions for the president on the obstruction issue. In March, Mueller raised the prospect of subpoenaing Trump if he refused to be questioned voluntarily.
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The letter was the latest step in ongoing negotiations between Mueller and the president's lawyers over a potential interview.
It is unclear if Trump will do so. "Kavanaugh actually has a long résumé", including a decade as a federal judge and years as a lawyer in the George W. Bush White House", Trevor Noah said on Tuesday's Daily Show.
According to a Tuesday in The New York Times, has shifted his position on whether he wants to answer questions under oath in a personal interview. You know, he's Comey's best friend.
"How can you possibly have a man who is that, and then somebody from his law firm came out and said, 'I can't believe they picked Mueller - he hates the president, he hates the president, '" Trump said.
And for another, Trump claimed, without any proof that Comey and Mueller are "best friends" and even more, of the "hugging and kissing" variety.