A deal has been brokered for Robert Mueller to testify to Congress about his report into Russian election interference and possible obstruction of justice by Donald Trump – an event that has immediately become the latest, most eagerly anticipated appearance of an official on Capitol Hill.

As it emerged Mr Mueller had written to the department of justice to say he did not believe attorney general William Barr’s four-page summary of his 450-page report correctly captured its context and content, a Democratic congressman said the 74-year-old special counsel would likely appear some time this month. It would be the first public appearance by Mr Mueller for more than two years.

The head of the House of Representatives’ judiciary committee, Jerry Nadler, told news agency Reuters it was important the former FBI director testified: “which they've agreed to do subject to setting a date, and we'll see if they do that, sometime in May.”

said that while the former FBI director was expected to testify at some point in May, no date had been set.

Mr Nadler also released the letter Mr Mueller sent to Mr Barr that asserted the attorney general’s snap summary of the Russia probe’s findings caused public confusion about critical aspects of the investigation.

Criminals who worked for Trump Show all 5 1 /5 Criminals who worked for Trump Criminals who worked for Trump Michael Cohen Former lawyer for Donald Trump was sentenced to three years in prison on counts involving evading income tax, false disclosure of the hush money paid to Stormy Daniels and another hush money charge Getty Criminals who worked for Trump Paul Manafort Former campaign manager for Trump Manafort was found guilty in February 2018 of five counts of tax fraud, two counts of bank fraud and one count of failure to disclose a foreign bank account. The crimes occurred prior to his appointment in Trump's campaign Getty Criminals who worked for Trump George Papadopoulos Former Trump campaign adviser Papadopoulos pleaded guilty to lying to the FBI in October 2017. He had lied about making contact with a professor who claimed that the Russians had dirt on Hillary Clinton. He was sentenced to 14 days in jail Getty Criminals who worked for Trump Michael Flynn Former White House National Security adviser Michael Flynn pleaded guilty to lying to the FBI in December 2017. He had lied about conversations that he had with the Russian ambassador to the US during Trump's Presidential campaign. He was not given prison time due to his "significant assistance" to the Mueller investigation Getty Criminals who worked for Trump Rick Gates Deputy chairman of Trump's presidential campaign Gates pleaded guilty to lying to the FBI in February 2018 AFP/Getty

In his letter, Mr Mueller raised concerns about a short summary that Mr Barr sent to Congress detailing what he said were Mr Mueller’s principal conclusions. The summary said Mr Mueller had not managed to reach a legal conclusion on whether the president had obstructed justice despite presenting evidence of occasions where Mr Trump may have impeded the investigation.

The summary was released two days after the Department of Justice (DoJ) received the special counsel’s report, which was several weeks before a redacted version of Mr Mueller’s 400-page report was released on 18 April.

In a letter dated 24 March, Mr Mueller said Mr Barr’s summary did not fully capture the context, nature and substance of the special counsel’s work and conclusions.

The special counsel told Mr Barr: “[This] threatens to undermine a central purpose for which the department appointed the special counsel: to assure full public confidence in the outcome of the investigations.”

Mr Mueller’s report revealed 11 instances where the behaviour of the president or officials related to his campaign might have amounted to obstruction. The report also said that the Trump campaign was “receptive” to assistance from Moscow during the 2016 election and expected to benefit from Russian interference.

Mr Mueller also wrote: “While this report does not conclude that the president committed a crime, it also does not exonerate him.”

Mr Mueller said in his report that he believed his hands were tied over criminal charges by DoJ rules that prevented a sitting president from facing such action. However, he made it clear that he did not exonerate Mr Trump of obstruction of justice but left the decision about whether to chase criminal charges to the attorney general. Mr Barr and his deputy, Rod Rosenstein, said that they believed the actions mentioned in the report did not rise to the level needed for a criminal prosecution.

As Mr Nadler announced the deal over Mr Mueller’s testimony, Mr Barr appeared before a Senate panel to face questions about his handling of the special counsel’s report amid accusations – particularly from Democrats – that Mr Barr had misrepresented the document’s findings.

Asked if he was happy for Mr Mueller to testify, he said the decision would be up to Mr Trump, but added: “I’ve already said I have no objection.”

Mr Barr defended the way he dealt with the report’s release and redactions – removing parts of the document to protect sensitive information – made by the DoJ. In prepared testimony to the senate judiciary committee hearing, he denied accusations that he has sought to protect Mr Trump.

At the outset of the hearing, the committee’s chairman, Republican Lindsey Graham – who has said that Mr Trump said to fight Democrat-led investigations into the report “like hell” – remarked that the report showed that congress should focus on protecting the coming 2020 election from foreign interference.

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“My takeaway from this report is we’ve got a lot to do to defend democracy against Russians and other bad actors,” Mr Graham said.

Mr Barr faced tough questions from Democrats on the committee, with senator Dianne Feinstein setting the tone.

“Contrary to declarations of total and complete exoneration, the special counsel’s report contained substantial evidence of misconduct,” Ms Feinstein, the committee’s top Democrat, said in opening remarks.