US President Donald Trump is facing a Congressional probe into possible obstruction of justice and abuse of power that could eventually lead to impeachment proceedings.

Declaring it was “very clear” Mr Trump obstructed justice, Jerrold Nadler, chairman of the House committee in charge of impeachment told US broadcaster ABC the panel was requesting documents from more than 60 people in the President’s administration, family and business as part of a rapidly expanding probe.

Mr Nadler said Monday morning (Australian time) the materials gathered would be used “to begin investigations to present the case to the American people about obstruction of justice, corruption and abuse of power”.

“Impeachment is a long way down the road. We don’t have the facts yet. But we’re going to initiate proper investigations,” he said.

“It’s our job to protect the rule of law,” he said, adding: “It’s very clear that the President obstructed justice.” 

As evidence of obstruction, Mr Nadler cited Mr Trump’s firing of former FBI Director James Comey, who at the time was leading an investigation into Russia’s alleged interference in the 2016 US presidential election and possible collusion between Trump’s campaign and Moscow.

That investigation was subsequently taken over by Special Counsel Robert Mueller, who is expected to deliver his findings to the US Attorney General within days.

Mr Nadler also cited what he called Mr Trump’s attempts to intimidate witnesses in the investigation.

He said the committee would release the list of people and organisations it would be requesting documents from on Monday local time.

Mr Trump responded by accusing the Democrats of an “abuse of power” by instituting the investigation.

“Look how they’re acting now and how we act when we’re in the majority. What the Democrats are doing is an abuse of power. They couldn’t find anything…they took a Fake Dossier & couldn’t find any Collusion. Now they have a fake witness in Cohen.” Congressman Mark Green, (R-TN).

— Donald J. Trump (@realDonaldTrump) March 3, 2019

The President earlier launched a fresh attack on Mr Mueller’s Russia investigation on Sunday, calling it a partisan probe unfairly aimed at discrediting his presidential win.

After more than two years of Presidential Harassment, the only things that have been proven is that Democrats and other broke the law. The hostile Cohen testimony, given by a liar to reduce his prison time, proved no Collusion! His just written book manuscript showed what he…..

— Donald J. Trump (@realDonaldTrump) March 3, 2019

“I am an innocent man being persecuted by some very bad, conflicted & corrupt people in a Witch Hunt that is illegal & should never have been allowed to start – And only because I won the Election!” he wrote.

Mr Trump’s political stocks have taken a hit in the last week, with the President returning empty-handed from a denuclearisation summit with North Korean leader Kim Jong-un, while his former lawyer Michael Cohen described him as a “con man” and “cheat” during a public Congressional hearing.

Cohen said Mr Trump knew of the damaging WikiLeaks email dump in advance. Photo: Getty

The President is already the subject of several House committee investigations into alleged coordination between Trump associates and Russia’s efforts to influence the 2016 US election, Mr Trump’s tax returns and possible conflicts of interest involving the Trump family business and policy-making.

The House oversight committee has also set a Monday deadline for the White House to turn over documents related to security clearances after The New York Times reported that the President ordered officials to grant his son-in-law Jared Kushner’s clearance over the objections of national security officers.

-with AAP