The president also offered mixed messages on Russia's efforts to help him defeat Democrat Hillary Clinton, first tweeting that he had "nothing to do with Russia helping me get elected," then minutes later, telling reporters: "Russia did not help me get elected."
Trump said Mueller, who is a Republican, was "conflicted" and should have investigated law enforcement officials who the president claims tried to undermine him. "Robert Mueller should have never been chosen," Trump said, adding falsely that Mueller wanted the FBI director job, but the president told him no.
"I think Mueller is a true never Trumper. He's somebody who didn't get a job that he wanted very badly." Mueller, who was appointed special counsel by Trump's Justice Department, was previously FBI director, appointed by Republican President George W. Bush.
Speaking to reporters on the White House South Lawn, Trump insisted that he's been tough on Russia and that Moscow would have preferred Hillary Clinton as president.
The special counsel's report said Russian interference in the election helped Trump defeat Clinton, Asked about impeachment by Congress, he called it a "dirty word" and said he couldn't imagine the courts allowing him to be impeached. "I don't think so because there's no crime," he said.
Mueller said Wednesday that charging Trump with any crime in court was "not an option" because of federal rules, but he used his first public remarks on the Russia investigation to emphasize that he did not exonerate the president. "If we had had confidence that the president clearly did not commit a crime, we would have said so," Mueller declared.
The special counsel's remarks on indicting Trump marked a counter to criticism, including by Attorney General William Barr, that Mueller should have reached a determination on whether the president illegally tried to obstruct the probe by taking actions such as firing FBI Director James Comey.
Mueller made clear that his team never considered indicting Trump because the Justice Department prohibits the prosecution of a sitting president.
"Charging the president with a crime was therefore not an option we could consider," Mueller said during a televised statement.
He said he believed such an action would be unconstitutional.