Leading US Democrats are calling for a report into alleged collusion between Donald Trump's 2016 presidential campaign and Russia to be fully published.

The confidential file by Special Counsel Robert Mueller has been sent to Attorney-General William Barr, who will send a summary to Congress.

The report is looking into Russian interference in the 2016 presidential election and possible collusion with Mr Trump's associates.

The Associated Press has said that the report is not recommending any further formal charges.

Other findings are unknown and it will be up to Mr Barr to decide how much will be made public.

Mr Barr has said he could update Congress as early as this weekend.

A Department of Justice official said the principal conclusions will be made public at that point.

White House spokeswoman Sarah Sanders said: "The next steps are up to Attorney General Barr, and look forward to the process taking its course. The White House has not received or been briefed on the special counsel's report."

The next steps are up to Attorney General Barr, and we look forward to the process taking its course. The White House has not received or been briefed on the Special Counsel’s report.

— Kayleigh McEnany 45 Archived (@PressSec45) March 22, 2019

But US House Speaker Nancy Pelosi and Senate Democratic leader Chuck Schumer have called for the report to be published in full now.

In a joint statement, they said: "Now that Special Counsel Mueller has submitted his report to the Attorney General, it is imperative for Mr Barr to make the full report public and provide its underlying documentation and findings to Congress.

"Attorney General Barr must not give President Trump, his lawyers or his staff any 'sneak preview' of Special Counsel Mueller's findings or evidence, and the White House must not be allowed to interfere in decisions about what parts of those findings or evidence are made public.

Speaker of the House Nancy Pelosi and Senate Minority leader Charles Schumer pose for photographs after delivering a televised response to President Donald Trump's national address about border security in January 2019 in Washington, DC | Image: Chip Somodevilla/DPA/PA Images

"The Special Counsel's investigation focused on questions that go to the integrity of our democracy itself: whether foreign powers corruptly interfered in our elections, and whether unlawful means were used to hinder that investigation.

"The American people have a right to the truth. The watchword is transparency."

Mr Trump's lawyers, Rudy Giuliani and Jay Sekulow, said they were "pleased" the report has been delivered and that Mr Barr "will determine the appropriate next steps".

Doug Collins, the top Republican on the House Judiciary Committee, said the report should be released to his committee and the public "without delay".

Mr Mueller has spent almost two years examining Russian interference in the 2016 presidential election.

He has looked into potential collusion between Trump associates and Russian agents working towards influencing the election, and whether efforts have been made to obstruct the investigation.

US Attorney-General William Barr, seen leaving his home in Virginia, will decide on the next steps | Image: Jose Luis Magana/AP/Press Association Images

Mr Mueller's remit initially extended to allegations of payments made to silence women who threatened Mr Trump's presidential campaign, before the special counsel handed it over to a separate team.

A number of people have already been claimed by the investigation - most recently seeing Mr Trump's former personal lawyer Michael Cohen turning his back on his old boss, calling him a "racist and a conman".

Mr Cohen admitted lying to Congress about Trump Organisation plans in Moscow as part of the investigation.

Some 34 people and three companies have been charged in connection to the Mueller investigation.

Among the high-profile figures are Mr Trump's former campaign chairman Paul Manafort, who has been sentenced to seven-and-a-half years behind bars.

Mr Trump's long-time adviser Roger Stone pleaded not guilty to seven charges and George Papadopoulos, a former Trump campaign foreign policy adviser, received a fine and short sentence for lying to the FBI.

On his appointment in May 2017, Mr Mueller resigned from his private law firm to avoid any conflicts of interest with firm clients or attorneys.

Additional reporting: IRN