President Donald Trump. Picture: Evan Vucci/AP/African News Agency (ANA)

Washington - US President Donald Trump said on Saturday investigators had found no evidence of collusion with Russia, a day after US prosecutors detailed a previously unknown attempt by a Russian to help his 2016 presidential election campaign.

Trump tweeted: "After two years and millions of pages of documents (and a cost of over $30 million) no collusion!"

The alleged Russian approach was outlined in one of several court filings Friday by US prosecutors in New York and Special Counsel Robert Mueller seeking prison time for Trump's former lawyer, Michael Cohen. He is to be sentenced next week for campaign finance violations, financial crimes and lying to Congress about Trump's business dealings in Russia.

During discussions about a possible hotel bearing Trump's name in Moscow, Cohen told prosecutors, he was approached in November 2015 by an unnamed Russian claiming to be a "'trusted person' in the Russian Federation," the filing said.

The Russian offered "synergy on a government level" with the Trump campaign in pushing for a meeting between Trump and Russian President Vladimir Putin, it continued, adding that Cohen said he did not follow up.

Mueller said that discussions about the potential Moscow development were relevant to his investigation because they occurred "at a time of sustained efforts by the Russian government to interfere with the US presidential election."

In a separate federal court filing on Friday, Mueller's office said that Trump's former campaign chairman, Paul Manafort, lied to investigators about his interactions with a Russian tied to Russian intelligence services.

That filing detailed why Mueller's office last week retracted a plea agreement with Manafort. He pleaded guilty in September to two conspiracy charges and agreed to cooperate with investigators in hopes of a lighter sentence.

Mueller is investigating whether there was collusion between Trump's 2016 presidential campaign and Russia, which US intelligence agencies charge mounted an influence operation to sway the vote to Trump over his Democratic rival, Hillary Clinton.

Russia denies interfering in the election to help Trump.

Reuters