According to the Washington Post newspaper, citing sources familiar with the matter, Trump's lawyers claimed during a meeting in March that Mueller had no obligation to talk with federal investigators over Russia's interference case, however, he said he saw no other option rather than to issue a subpoena for Trump to appear before a grand jury.
John Dowd, then the president’s lead lawyer, met the warning with a sharp response, saying it was not a game and that thus Mueller was "screwing with the work of the president of the United States," according to the newspaper.
Mueller's team provided a list of dozens of questions that the federal investigators wanted to discuss with Trump, according to the newspaper. The questions related to US high-level firings, the election campaign and Trump's business, leaked to the media, a fact that Trump called "disgraceful."
Russian officials have repeatedly denied allegations of interference in the US election, calling the accusations "absurd." Trump has also denied any collusion between himself and the Kremlin and has called Mueller's investigation a "witch hunt."