US attorney general William Barr has told legislators they could expect a redacted copy of special counsel Robert Mueller’s report “within a week”.

Mr Barr was speaking about the report – the findings of an investigation into alleged Russian interference in the 2016 election and possible links collusion with Donald Trump’s 2016 campaign – during a tense hearing on Capitol Hill that yielded more questions than answers.

The attorney general abruptly declined to answer further questions about the investigation halfway through the hearing, saying: “I’ve said what I was going to say about the report today.” He then refused to answer whether the White House had been briefed on any aspect of the special counsel’s report.

“I’m not going to say anything more about it until the report is out,” he added.

Democrats expressed frustration and concern with Mr Barr’s handling of the report. Nita Lowey, chair of the House Appropriations Committee grilled him over how he managed to reduce the massive document into four pages just days after he had received it.

“Even for someone who has done this job before, I would argue it’s more suspicious than impressive,” she said.

Mueller investigation: The key figures Show all 12 1 /12 Mueller investigation: The key figures Mueller investigation: The key figures Robert Mueller is the special counsel overseeing the investigation into Russia's meddling in the 2016 election, and potential obstruction of justice by the president. Mr Mueller has a pristine reputation in Washington, where he was previously in charge of the FBI. Throughout his investigation, he and his team have been notoriously tight lipped about what they know and where their investigation has led. REUTERS Mueller investigation: The key figures Former FBI director James Comey was the catalyst that led to the appointment of special counsel Robert Mueller. Mr Comey was fired by the president after Mr Trump reportedly asked him to drop his own Russia investigation. Mr Trump has long maintained that the investigation is a "witch hunt". AFP/Getty Images Mueller investigation: The key figures Deputy attorney general Rod Rosenstein had authority over the special counsel investigation for much of the two years it has been active. Mr Rosenstein found himself with that responsibility after then-attorney general Jeff Sessions recused himself from that oversight. AP Mueller investigation: The key figures Attorney general Jeff Sessions's decision to recuse himself from oversight of the special counsel investigation may have cost him his job in the end. Mr Sessions resigned last year, after weathering a contentious relationship with Donald Trump who vocally criticised his attorney general for taking a step back. Mr Sessions recused himself from the oversight citing longstanding Justice Department rules to not be involved in investigations overseeing campaigns that officials were apart of. AP Mueller investigation: The key figures Attorney General William Barr is currently responsible for oversight of the special counsel investigation. Mr Barr's office will be the first to receive the Mueller report when it is finished. His office will then determine what portion or version of that report should be delivered to Congress, and also made public. EPA Mueller investigation: The key figures Michal Cohn is the president's former personal lawyer, who has been helping the special counsel investigation as a part of a plea deal over financial crimes, and campaign finance crimes, he has pleaded guilty to. Among those crimes, Cohen admitted to facilitating $130,000 in hush money payments to adult film actress Stormy Daniels during the 2016 campaign. Cohen has said he did so at the direction of Mr Trump. Cohen has also admitted that he maintained contacts with Russian officials about a potential Trump real estate project in Moscow for months longer than Mr Trump and others admitted. The talks continued well into 2016 during the campaign, he has said. AP Mueller investigation: The key figures Stormy Daniels has alleged that she had an affair with Donald Trump in 2006, soon after Melania Trump gave birth to Baron Trump. The accusation is of particular importance as a result of the $130,000 hush money payment she received to keep quiet about the affair during the 2016 campaign. AP Mueller investigation: The key figures Paul Manafort was Donald Trump's former campaign chairman. Manafort was charged alongside Rick Gates for a slew of financial crimes, and was convicted on several counts in a Virginia court. He then pleaded guilty to separate charges filed in a Washington court. Manafort has been sentenced to just 7.5 years in prison for his crimes — in spite of recommendations from the special counsel's office for a much harsher sentence. AP Mueller investigation: The key figures George Papadopoulos was one of the first individuals associated with the Trump campaign to be charged by the Mueller probe. He ultimately received a 14 day prison sentence for lying to investigators about contacts he had with Russian officials. AP Mueller investigation: The key figures Roger Stone is a well known political fixer and operative, who has made a name for himself for some dirty tactics. He has been charged by the Mueller probe earlier this year, and he has been said to have had prior knowledge that WikiLeaks planned on publishing stolen emails from the Hillary Clinton campaign in 2016. Getty Images Mueller investigation: The key figures Rick Gates was charged alongside former Trump campaign chairman Paul Manafort for a range of crimes. Gates, who worked alongside Manafort for a pro-Russia Ukrainian political party. The two were charged with conspiracy and financial crimes. Gates pleaded guilty. AP Mueller investigation: The key figures Former national security adviser Michael Flynn was one of the first casualties of the Russia scandal, and was forced out of his position in the White House weeks after Donald Trump took office. Flynn pleaded guilty in 2017 to "willfully" making fraudulent statements about contacts he had with Russian officials including former Russian ambassador to the US Sergey Kislyak. Flynn then lied to Vice President Mike Pence about that contact. REUTERS

Mr Barr acknowledged his quick work, claiming: “The thinking of the special counsel was not a mystery to the department of dustice prior to the submission of the report.” He added that Mr Mueller’s team was redacting the report before providing it to Congress.

The attorney general said he plans to produce a report during “this first go” with four types of redactions – relating to grand jury information, classified information that could reveal agency sources or methods, information pertaining to ongoing prosecutions, and information that may implicate “privacy or reputational interests” of peripheral players.

The report will be colour-coded, according to Mr Barr, and will feature explanatory notes for all of his redactions. It remains unclear what legal grounds the attorney general has to place redactions for all four of his listed components, however.

Mr Barr added he would convene with Republican and Democratic leadership from the House judiciary committee after the report is released to determine whether they required any further information. Legislators may also request grand jury information from the courts, he said – a move he noted the justice department would not be making under his leadership.

The attorney general was brought to the house committee to discuss Mr Trump's budget request for the justice department for 2020. This was the central focus of Mr Barr’s opening statement and he did not at any point mention the Mueller report.

At times, there appeared to be two testimonies taking place. As Democrats grilled the attorney general over the special counsel’s conclusions, Republican lawmakers asked Mr Barr about his department’s plans surrounding issues including human and sex trafficking, and immigration along the US-Mexico border.

The Mueller report wasn’t the only thing Democrats flagged up, however. The hearing provided some tense moments when they grilled Mr Barr over the justice department’s opposition to the Affordable Care Act in federal courts under Mr Trump.

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