WASHINGTON (Reuters) - U.S. President Donald Trump on Saturday renewed his call to end a federal probe into Russian election meddling, describing the investigation as a “witch hunt” a day after U.S. prosecutors detailed a previously unknown attempt by a Russian to help his 2016 presidential election campaign.

“Time for the Witch Hunt to END!” Trump said in a message on Twitter. His tweet also quoted television host Geraldo Rivera, a Trump friend, dismissing any claim of collusion between the Trump campaign and Russia as “collusion illusion”.

It was the president’s second tweet of the day about Special Counsel Mueller’s investigation into Russian interference in the 2016 presidential election and whether Trump’s campaign colluded with Russia. Russia denies meddling allegations.

“After two years and millions of pages of documents (and a cost of over $30 million) no collusion!” Trump tweeted earlier on Saturday.

He repeated that contention later as he left the White House for the annual Army-Navy game in Philadelphia, saying, “We’re very happy with what we are reading, because there was no collusion whatsoever.”

U.S. prosecutors, however, did not address in several federal court filings on Friday the question of whether they have found collusion between the Trump campaign and Russia.

Moreover, Mueller said in one filing that Trump’s former lawyer, Michael Cohen, had provided his office with “useful information concerning certain discrete Russia-related matters core to its investigation that he obtained by virtue of his regular contact” with Trump’s real estate company during the 2016 campaign.

Democrats and other Trump critics fear that newly appointed acting Attorney General Matthew Whitaker, a Trump loyalist, could fire Mueller or undermine the investigation by cutting off its funding. Prominent Republicans in Congress insist that there is no danger of interference.

Trump said on Friday that he would nominate former Attorney General William Barr to the nation’s top law enforcement job. But with the current session of Congress set to end soon, Barr may have to wait until well into 2019 to be confirmed by the Senate.

In his court filing on Friday, Mueller said Cohen told them he was approached in November 2015 by an unnamed Russian claiming to be a “‘trusted person’ in the Russian Federation”. The filing said the contact occurred during discussions about a possible hotel bearing Trump’s name in Moscow.

Cohen is to be sentenced next week for campaign finance violations, financial crimes and lying to Congress about Trump’s business dealings in Russia. Prosecutors are seeking a substantial prison sentence.

Trump’s current lawyer, former New York Mayor Rudy Giuliani, also took aim at Cohen in a Saturday tweet, saying that federal prosecutors in New York are seeking a prison sentence for Cohen “because as we have said he’s still lying.”

Mueller said the Russian national who approached Cohen offered “synergy on a government level” with the Trump campaign in pushing for a meeting between Trump and Russian President Vladimir Putin, adding that Cohen said he did not follow up.

Mueller said that the discussions about a potential Trump hotel in Moscow were relevant to his investigation, because they occurred “at a time of sustained efforts by the Russian government to interfere with the U.S. presidential election.”

In a separate federal court filing on Friday, Mueller’s office said 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.