US President Donald Trump could face impeachment and jail if hush money payments reported by his former lawyer are proven to be campaign finance violations, Democrats warn.
Court filings on Friday in cases stemming from a federal probe into Russian activities during the 2016 presidential election pointed to potential problems for Trump, including whether he instructed six-figure payments to two women during the campaign to keep quiet about affairs.
Federal prosecutors sought prison time for longtime Trump "fixer" Michael Cohen for paying off an adult film star and a former Playboy model at Trump's behest, evading taxes and lying to Congress about a proposed Trump Organization building in Moscow.
If the payments are proven to be felony campaign finance violations, Democratic US Representative Jerrold Nadler told CNN those would be grounds for impeachment.
"Well, they would be impeachable offences. Whether they are important enough to justify an impeachment is a different question," said Nadler, who will lead the Judiciary Committee when Democrats take control of the House of Representatives in January.
Under US law, campaign contributions, defined as things of value given to a campaign to influence an election, must be disclosed. Such payments are also limited to $US2700 ($A3,750) per person.
White House press secretary Sarah Sanders said on Friday Cohen had lied repeatedly and that the filing was insignificant.
Friday's filings also revealed new information about contacts between people working for Trump and Russians in the cases of Cohen, Trump's former longtime personal lawyer, and Paul Manafort, Trump's short-lived campaign chairman convicted in August of fraud.
Special Counsel Robert Mueller said Manafort lied to investigators about his interactions with a Russian tied to Russian intelligence services.
Mueller's office said the lying prompted prosecutors last week to retract a plea agreement with Manafort on two separate conspiracy charges.
"I think what these indictments and filings show is the president was at the centre of a massive fraud - several massive frauds - against the American people," Nadler told CNN.
Mueller is investigating Russian interference in the 2016 presidential election and whether Trump's campaign colluded with Moscow to sway the election. Russia denies interfering and Trump denies any collusion.
The investigation has cast a shadow over Trump's presidency, with its implication Moscow may have had a hand in his White House victory.
The Republican president repeatedly has expressed his impatience with the probe that Mueller took over in March 2017, saying it was politically motivated.
"Time for the Witch Hunt to END!" he said in a Twitter post on Saturday.
However the end of the Mueller probe could be the beginning of bigger problems.
"There's a very real prospect that on the day Donald Trump leaves office the Justice Department may indict him, that he may be the first president in quite some time to face the real prospect of jail time," Representative Adam Schiff, the Democrat who will lead the House Intelligence Committee next year, told CBS."
