The chairman of the House Judiciary Committee, Jerrold Nadler, on Thursday called Special Counsel Robert Mueller, who had headed the independent investigation into alleged links between Russia and President Donald Trump's 2016 campaign team, to testify before Congress "no later than May 23."

"As I have already communicated to the Department of Justice, I request your testimony before the Judiciary Committee as soon as possible - but, in any event, no later than May 23, 2019," Nadler wrote in a letter sent on Thursday morning to Mueller, which the lawmaker posted on his Twitter account.

In his tweet, Nadler said that "It is clear Congress and the American people must hear from Special Counsel Robert Mueller in person to better understand his findings," which - according to US Attorney General William Barr - determined that neither Trump nor anyone on his campaign staff collaborated or colluded with the Kremlin in 2016 to try and ensure his election.

Nadler's official call to Mueller to appear before Congress came just before the Justice Department sent to Congress a redacted version of the special counsel's report, which took almost two years to prepare.

The redacted version of the 400-page report is being made public on Thursday and Barr promised in a press conference before sending it to Congress that the "limited ... redactions" were designed not to interfere with the work of the intelligence community - by releasing classified information - or with the legal cases currently under way.

Barr said on Thursday morning that Mueller did not find "any evidence" that Trump obstructed justice in the Russia probe and insisted several times that there was "no collusion" with Russia by the president either before or after he was inaugurated.

The attorney general acknowledged that "earlier this week, the president's personal counsel requested and were given the opportunity to read a final version of the redacted report before it was publicly released."

However, he said that Trump did not exercise his right to invoke "executive privilege" to censure portions of the report remained secret and nobody outside the Justice Department edited the document or requested that it be edited.

At his press conference, Barr said that he did not have any objection to Mueller testifying before Congress, something that Democrats have been calling for for weeks.

Speaker of the House Nancy Pelosi, a Democrat, said Thursday that it is "more urgent than ever" for Mueller to offer his testimony before Congress regarding his investigation and conclusions after Barr admitted that Trump's legal team had been allowed to see the report before it was released to Congress or the public.