U.S. President Donald Trump on Wednesday called on Attorney-General, Jeff Sessions, to end a federal investigation into Russian interference in the 2016 presidential election and whether there was any cooperation by his campaign with Moscow.

Trump, who has long complained about the criminal probe into his White House victory, said the idea that his campaign worked with Moscow was a “Total Hoax” in a series of tweets aimed at undermining the integrity of Special Counsel Robert Mueller’s investigation.

In what appeared to be his most direct call for shutting down the probe, Trump wrote on Twitter: “This is a terrible situation and Attorney-General Jeff Sessions should stop this Rigged Witch Hunt right now before it continues to stain our country any further.

“Bob Mueller is totally conflicted,” Trump continued.

He provided no evidence that the team led by Mueller, a Republican appointed by Republicans, is biased against him.

The first trial arising from the probe into Russia’s role in the election began on Tuesday in Alexandria, Virginia.

Trump’s former campaign chairman, Paul Manafort, faces 18 counts of bank and tax fraud charges.

A Justice Department spokeswoman said the department had no immediate comment on Trump’s tweet about ending Mueller’s probe.

The Republican president has steadily attacked his attorney-general for recusing himself from the Russia probe in March 2017.

Sessions cited his role as a senior adviser to Trump’s presidential campaign and appointed Deputy Attorney-General, Rod Rosenstein, to oversee the investigation.

Rosenstein, in turn, appointed Mueller and is the person with the authority to fire him.

An element of Mueller’s investigation includes whether Trump or anyone in the campaign tried to obstruct justice.

The New York Times reported that the Mueller team was examining negative tweets and statements by Trump about Sessions and former FBI Director, James Comey.

The man heading Trump’s re-election campaign, Brad Parscale, has in recent months called on Trump to fire Sessions and end the Mueller probe.

U.S. intelligence agencies concluded in 2017 that Moscow meddled in the 2016 presidential campaign to try to tip the vote in Trump’s favour.

Moscow has denied such interference and Trump has denied any collusion by his campaign or any obstruction of justice.

Trump calls conservative Koch donors ‘total joke’.

He also said the charges against Manafort have nothing to do with Russia collusion.

Manafort worked for pro-Russian politicians in Ukraine.

While prosecutors have said they will not present evidence in this trial about possible collusion between Russia and the Trump campaign, they may dig deeper into Manafort’s connections with Russian and Ukrainian oligarchs, legal experts have said.