New information on the Russia investigation is expected Friday, with the special counsel Robert Mueller facing deadlines to publish new documents related to it.

Mueller is expected to submit important filings about Michael Cohen and Paul Manafort, the former personal attorney to and the former campaign chairman of President Donald Trump.

Former FBI Director James Comey is also set to testify Friday about the FBI's handling of the investigation into Russian interference in the 2016 election.

Comey, seen as a key witness into whether Trump attempted to obstruct the investigation, has negotiated a deal that lets him speak publicly about the closed-door interview.

Friday could prove a huge day for the investigation into Russian meddling in the 2016 US elections as deadlines arrive for the special counsel Robert Mueller to drop more documents on two key figures.

At the same time, former FBI Director James Comey is scheduled to testify in front of Congress in a closed-door interview he has nonetheless secured permission to speak about in public.

Comey, who was overseeing the FBI's Russia investigation when President Donald Trump fired him in May 2017, is believed to be at the center of the special counsel's inquiry into whether Trump obstructed justice in connection to the investigation.

Mueller is expected to submit several important filings related to the Russia investigation to meet a deadline on Friday.

The documents are believed to detail the cooperation of Trump's former personal lawyer Michael Cohen and what the special counsel's team has described as lies that led to the collapse of the plea deal by the former Trump campaign chairman Paul Manafort.

Mueller is expected to submit his sentencing recommendation for Cohen, who pleaded guilty in November to lying to Congress about a Russian real-estate project Trump pursued during the 2016 presidential campaign. Trump has sought to discredit Cohen as a credible source of information.

Michael Cohen, the former personal attorney to President Donald Trump, leaving federal court in November after pleading guilty to making false statements to Congress. Drew Angerer/Getty Images The special counsel's team is also set to disclose what it says are the "crimes and lies" of Manafort. He has been accused of lying to the FBI and to Mueller's office in violation of his plea deal.

Read more: Trump fires off late-night tweetstorm on the eve of a landmark moment in the Russia investigation

Previously, Mueller has said only that Manafort lied "on a variety of subject matters" and that the special counsel's office would provide further information in a later filing.

The Wall Street Journal reported in November that Mueller thought Manafort lied about his lobbying income and meeting with a Russian-Ukrainian political operative.

It is possible that Mueller's filings on Friday will be heavily redacted, as was the case with Mueller's sentencing memo for the former national security adviser Michael Flynn released Tuesday.

Read more: Mueller filing reveals Michael Flynn interviewed with investigators 19 times and recommends no jail time

Trump continues to lash out at the investigation. He repeated his common refrain of "witch hunt" in a series of tweets on Friday morning, which followed a firestorm of tweets on Thursday night. Trump has previously suggested he might pardon Manafort.

As well as the Mueller filing, more information may come out against Trump on Friday as Comey testifies to the House Judiciary Committee. The testimony is scheduled to take place in private, but, under a deal struck with the committee, Comey will be free to speak about the questioning after the interview. A transcript will also be released.

Comey is expected to discuss the FBI's handling of the Russia investigation as well as the investigation into former Secretary of State Hillary Clinton's use of a private email server.

Trump has said on national television that "this Russia thing" had been a factor in his decision for firing Comey.

Trump tweeted on Friday morning that "Robert Mueller and Leakin' Lyin' James Comey are Best Friends" and claimed it was a "conflict of interest" for Mueller.

Comey has previously compared outreach by the president and his circle to that of a mob boss and has said Trump was known for "lying about all things" and had a need for "complete control."