Mr Trump did not testify in the Mueller investigation, but he did submit written responses to some questions from the Mueller team.
During Mr Mueller's testimony before Congress in July, he was asked whether Mr Trump's incomplete written responses showed he was not always telling the truth. Mr Mueller replied: "I would say, generally."It is unclear what exactly Mr Mueller meant by his response,
He believed? Or did he hear it from somebody's cousin who said his Aunt Hillary told him?
US media report Mr Letter may have been referring to whether Mr Trump lied about contacts with WikiLeaks and knowledge that they were going to publish hacked Democratic emails.