Prosecutor says Trump is not exempt from investigation into Russia

"If we had the confidence that the president did not commit a crime, we would have said that," said Robert Mueller

US Special Prosecutor Robert Mueller said on Wednesday that his report of an investigation into a supposed collusion of Donald Trump 's campaign with Russia in 2016 did not relieve the president of responding to crimes. He said, however, that the country's constitution prevents him from making any formal accusation against the Republican.

"If we had the confidence that the president did not commit a crime, we would have said that," Mueller said in his first statement since starting two years ago on Moscow's interference in the 2016 US elections.

"Accusing the president for a crime ... was not an option we could consider," he told reporters. "We concluded that we could not come to a determination in one way or another about the president having committed a crime."

Mueller said the written report "speaks for itself" and that the special office for the investigation of the case will be officially closed. With this, he also announced his resignation from the Justice Department.

"Under the policy of the [Justice] Department, a president can not be charged with a federal crime while in office," he said. "This is unconstitutional," he said.