If Trump is subpoenaed to testify, Giuliani has said he would take Mueller to court.
Earlier Monday, Trump weighed in on the question of whether he could pardon himself for any crimes he might have committed. He wrote online that he will comply with Mueller probe despite his concerns about its constitutionality because, he said, he is innocent of any wrongdoing.
Trump cited "numerous legal scholars" in claiming the power to pardon himself, but there does not appear to be consensus on that point.
In recent weeks, Mueller's team also started the process of sentencing George Papadopoulos, a Trump campaign aide who pleaded guilty previous year to lying to investigators.
USA tariffs make China trade issues more hard to resolve
Earlier in March, Trump had announced the said tariffs to be applicable worldwide while exempting Canada , Mexico and the EU. The EU has said it would respond with tariffs on $3.3 billion in American imports as early as June 20 .
Giuliani reveals what Trump will do about Jeff Sessions - and when
Comey documented conversations with Trump in the weeks leading up to his dismissal in a series of memos. Bharara said that during the transition, Trump asked him to stay on during a meeting at Trump Tower.
North Korean official Kim Yong Chol arrives at White House
Donald Trump's summit with Kim Jong-un in Singapore on 12 June is back on, the USA president says, a week after it was scrapped. The State Department official said they were seeking a corresponding commitment and "action" from the North Koreans.
Sanders said the same when asked whether Trump has consulted with the Office of Legal Counsel on his pardoning power.
Giuliani wasn't the only Republican against the idea of Trump issuing a self-pardon.
The US president is being investigated to establish whether there was collusion between Russian Federation and the Trump campaign during the 2016 US election. In that tweet, he insisted that "we play the game because I, unlike the Democrats, have done nothing wrong!".
Trump tweets on Monday: "The appointment of the Special Councel is totally UNCONSTITUTIONAL!" Instead, Giuliani said, Trump would have to be impeached.
Among those who have pleaded guilty are former Trump national security adviser Michael Flynn and Rick Gates, a longtime business partner of Paul Manafort, the former Trump campaign chairman who has been indicted in the investigation. "The president never said he pardoned himself", he said on CNN's State of the Union. "It is hard to imagine judicial backing of these views", said Mark Rozell, dean of the Schar School of Policy and Government at George Mason University and author of a book on presidential powers.