It is the first time the USA leader has directly co-operated with the investigation he has long decried as a "witch-hunt", with some fearful that his post-midterms sacking of attorney general Jeff Sessions would lead to an attempt to bring the inquiry to an end.
Investigators months ago presented Trump's legal team with dozens of questions they wanted to ask the president related to whether his campaign coordinated with the Kremlin to tip the 2016 election and whether he sought to obstruct the Russian Federation probe by actions including the firing of former FBI Director James Comey.
The precise questions and answers that Trump gave to Mueller weren't immediately clear, though the president told reporters last week that he had prepared the responses himself.
"I feel like I'm back in seventh grade here, where we have juvenile name-calling", said Congressman Mike Quigley, a Democrat from IL and member of the House intelligence committee, on CNN's New Day. He vowed to take action against Acting Attorney General Matt Whitaker if he intervenes to halt Special Counsel Robert Mueller's probe.More news: At least three people dead after shooting and fire at huge mansion
Mueller was tasked to probe "any matters that arose or may arise directly from the investigation" into possible collusion between Trump's campaign and Russian Federation during the 2016 election.
Trump's lawyers say it's time for the investigation to end, but Mueller's team may well press for additional information.
Mueller has already brought charges against some former Trump aides, including his former campaign chairman and his former national security adviser, as well as a number of Russian individuals and entities.
President Trump attacked California Democratic Congressmember Adam Schiff Sunday, misspelling his last name.More news: President Trump pardons a turkey
Giuliani later told Reuters there was "very little hope" Trump would sit for an interview with the special counsel.
Trump's response comes after a protracted period of negotiations between his attorneys and Mueller's team over the scope of the questions he would respond to.
"I write the answers".
After his appointment, Senate Democrat leader Chuck Schumer said the president risked creating a "constitutional crisis" if he sought to impede the Mueller investigation. As a private citizen, Whitaker criticized the Mueller probe. "We're talking about protecting the rule of law, and the best the president can do is start calling people names".More news: Djokovic overcomes illness to beat Zverev at ATP Finals