The news emerges as experts warn that Russia has already embarked on an influence campaign to manipulate upcoming European elections. Present Donald Trump, who has always denied collusion with Moscow, remained uncharacteristically quiet yesterday as he played golf at his Mar-a-Lago resort in Florida. However on Wednesday he challenged Mr Mueller to publish the full report, adding: “Let it come out, let people see it. Let’s see whether or not it’s legit.”
His call was backed by Congress, with the House of Representatives unanimously voting for the entire report to be published.
However, under Department of Justice regulations, how much detail is ultimately disclosed rests with US Attorney General William Barr.
Last night he promised “as much transparency as possible”.
Mr Mueller investigated whether the Trump campaign conspired with Moscow to try to influence the election and whether the President later unlawfully tried to obstruct his investigation.
It followed warnings by US intelligence agencies that Moscow ran a campaign of email hacking and online propaganda aimed at sowing discord in the US, hurting Democratic candidate Hillary Clinton and helping Mr Trump.
Moscow also denies the claims.
The investigation has produced scalps, however, with 34 people and three companies charged.
Some former Trump aides were given prison sentences, including former campaign chairman Paul Manafort, national security adviser Michael Flynn and personal lawyer Michael Cohen.
Mr Cohen implicated the president in his guilty plea on campaign finance violations in a separate prosecution brought by federal prosecutors in New York. None of those charges, however, directly related to the question of whether there was collusion between the Trump campaign and Moscow.
But last night US Justice Department sources confirmed that no new indictments would be forthcoming as a result of this investigation.
The main findings are expected to be made public this weekend.