Thursday marked one year since Mueller was named special counsel in the investigation into Russian interference in the election and the Trump campaign's alleged ties to Moscow.

President Donald Trump rang in the one-year anniversary of the appointment of special counsel Robert Mueller by slamming the probe into his campaign's ties to Russian during the 2016 election.

"Congratulations America, we are now into the second year of the greatest Witch Hunt in American History...and there is still No Collusion and No Obstruction," Trump tweeted. "The only Collusion was that done by Democrats who were unable to win an Election despite the spending of far more money!"

Thursday marked one year since Deputy U.S. Attorney General Rod Rosenstein appointed Mueller, a former FBI director, to be a special counsel overseeing the investigation.

 Following Mueller's appointment, Trump said he looked forward "to this matter concluding quickly."

"As I have stated many times, a thorough investigation will confirm what we already know — there was no collusion between my campaign and any foreign entity," he said in the May 17, 2017, statement. "I look forward to this matter concluding quickly. In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country."

The probe has not gone as he'd predicted.

Since Mueller's appointment, nearly 20 individuals have been charged with crimes, including five who pleaded guilty (among them Michael Flynn, the former national security adviser) and 13 Russian nationals.

Trump has repeatedly ripped the probe as a "witch hunt" and has reshuffled his legal team multiple times. Earlier this month, Trump tapped Emmet Flood, who advised Bill Clinton during his impeachment proceedings, to assist in the Russia investigation. And last month, he brought on former New York Mayor Rudolph Giuliani, a longtime Trump ally and ex-federal prosecutor in New York, to provide advice on how to deal with the special counsel's probe.

How — or when — the probe will end, however, remains unclear.

Giuliani said Wednesday that Mueller's office had told Trump's legal team that he won't indict a sitting president.

"They (the special counsel's office) acknowledge the fact that they can't indict us," Giuliani told NBC News, indicating that the information had been conveyed to Trump's lawyers. "They know they don't have that power. So their function is to write a report. We would like it to be the fairest report possible. But even if it isn't, we're prepared to rebut it in great detail, so we'd like them to do it."

He added: "It's as clear as can be that they don't have the right to indict under the Justice Department rules. And I know they're not going to indict."Giuliani also suggested Wednesday that Mueller may not even interview Trump.