Trump attacks Russia probe ahead of new Mueller reports

US President Donald Trump unleashed a series of attacks Friday on US Special Counsel Robert Mueller and his team, with the prosecutor expected to release documents that could shed new light in the Russia probe.

Repeating his regular dismissal of the probe as a "total witch hunt," Trump accused Mueller of political bias in an early morning tweetstorm alleging that the prosecutor had coerced false testimony from witnesses.

He complained that investigators were ignoring Democrats' dealings with Russians and suggested his own deputy attorney general was "totally conflicted." Trump's tweets came with Mueller's team expected to file court documents related to two pivotal figures in their probe into possible collusion between Trump's campaign and Russia to swing the 2016 election: former Trump campaign chairman Paul Manafort and the president's ex-lawyer Michael Cohen.

"Robert Mueller and Leakin' Lyin' James Comey are Best Friends, just one of many Mueller Conflicts of Interest," Trump tweeted, referring to the former FBI chief he sacked while Comey was leading the Russia probe.

Trump has repeatedly disparaged the 19-month-old investigation but ratcheted up his attacks as the probe in recent weeks appeared to leave him increasingly under pressure.

Among five tweets, Trump also attacked Deputy Attorney General Rod Rosenstein, who was in charge of the probe until Trump in November named Matthew Whitaker, who had criticized Mueller's investigation, as acting attorney general.

Trump asked whether Rosenstein isn't "totally conflicted," while also singling out a member of Mueller's team, Andrew Weissmann, who has been involved in the prosecution against Paul Manafort.

On Friday, the special counsel's team was expected to provide court with details of Manafort's lying to investigators.

Manafort chaired the Trump election campaign from March until August 2016. In September this year he admitted financial crimes related to his work before 2015 for Russia-supported Ukrainian politicians, and agreed to cooperate with Mueller's probe.

But last week the special counsel's office said Manafort had violated his plea deal by lying. Also on Friday, prosecutors were expected to file more details about the cooperation which Trump's ex-lawyer Michael Cohen has provided the special counsel.

Cohen has admitted lying to Congress about pursuing a real estate deal with Russia on Trump's behalf.

Comey is to testify behind closed doors Friday to the House Judiciary Committee, which is conducting a Republican-driven probe into the conduct of law enforcement officials.

Mueller has already charged more than 30 individuals, most of them Russians.

Among those pleading guilty in the Mueller probe is Michael Flynn, Trump's first national security advisor. Mueller reported this week that Flynn has given "substantial assistance" to the investigation and should serve no jail time.