US Special Counsel Robert Mueller said on Wednesday that he is leaving the Justice Department now that he has concluded his Russia probe.
In his first public statement on the investigation into Russian interference in the 2016 election, Mueller said he is also closing the special counsel's office.
The announcement comes amid demands for Mueller to testify on Capitol Hill about his findings and tension with Attorney General William Barr over the handling of his report.
Mueller said on Wednesday that the report is his testimony. He said that he hopes and expects that Wednesday is the "the only time" that he speaks about the report, but "any testimony from [his] office would not go beyond the report".
A redacted version of the Mueller report was published in April, concluding there was no conspiracy between the Trump campaign and Moscow. But Mueller declined to make a judgment on whether President Donald Trump obstructed justice, though the report outlined 10 instances in which Trump tried to impede the investigation.
Barr and former deputy Attorney General Rod Rosenstein subsequently determined Trump had not broken the law.
Mueller said on Wednesday that charging Trump was never an option for his team of prosecutors, citing Justice Department guidelines that prohibit charging a sitting president.
"Charging the president with a crime was ... not an option we could consider," Mueller told reporters.
"We concluded that we would not reach a determination one way or the other about whether the president committed a crime," he said. "If we had confidence that the president clearly did not commit a crime, we would have said so. We did not, however, make a determination as to whether the president did or did not."
Shortly after Mueller's announcement, Trump tweeted that "nothing changes".
"The case is closed! Thank you," Trump said.
White House Press Secretary Sarah Sanders said in a statement that "the report was clear - there was no collusion, no conspiracy - and the Department of Justice confirmed there was no obstruction."
She added, "After two years, the special counsel is moving on with his life, and everyone else should do the same."
Democrats, who control the House of Representatives, and Trump are engaged in a high-stakes power struggle over their ability to investigate him, with the president stonewalling multiple investigations by congressional committees.
The probes range from whether Trump obstructed justice during Mueller's investigation to his personal finances and businesses.
Earlier this month, Trump invoked executive privilege to block the release of the full, unredacted version of the Mueller report.
Trump has also said Mueller should not testify before Congress but that the final decision was up to Barr. Democrats have denounced Barr, saying he misrepresented the special counsel's findings.
Jerrold Nadler, the chairman of the House Judiciary Committee, on Wednesday, vowed to hold Trump accountable for his "crimes and lies".
"It falls to Congress to respond to the crimes, lies and other wrongdoing of President Trump" given that Mueller was unable to pursue charges against him, Nadler said in a statement.
Nadler is set to hold a press conference later on Wednesday.