The report covers Mueller's probe of Russian interference in the 2016 presidential campaign and actions by President Donald Trump and his campaign
US House Judiciary Committee Chairman Jerrold Nadler said on Monday that Attorney General William Barr must testify before his panel on Thursday, despite Barr's reported objections to a more aggressive format for questions planned by Democrats.
"We've been very clear. Barr has to come. He has to testify. It's none of the business of a witness to try to dictate to a congressional committee what our procedures for questioning him are," Nadler told reporters.
"He is supposed to show up on Thursday and we will take whatever action we have to take if he doesn't," he added.
Justice Department officials had no immediate comment on the lawmaker's remarks.
A Democratic congressional aide on Sunday said that Barr might skip the hearing because he objects to plans for an extra hour of questioning that would include committee lawyers, and a closed session to discuss classified sections of US Special Counsel Robert Mueller's Russian investigation report.
The report covers Mueller's probe of Russian interference in the 2016 presidential campaign and actions by President Donald Trump and his campaign.
It details a series of actions by Trump to impede the Russia probe. It did not conclude whether those actions constituted the crime of obstruction. But it did conclude that Trump and his campaign had not engaged in a criminal conspiracy with Moscow. Barr, a Trump appointee, released a redacted version of the document on April 18.
Nadler has subpoenaed the full document and demanded that the Justice Department provide it and underlying evidence by 1400 GMT on Wednesday. After meeting with Justice Department officials earlier on Monday, the chairman said he expects the administration to adhere to the deadline.
Republicans on Nadler's committee have sided with the attorney general, saying the demands are unreasonable.
But Democrats say the new format is necessary to ensure that witnesses answer the questions posed. The traditional hearing format gives each lawmaker five minutes for questions. But Democrats say Trump administration officials have become adept at running out the clock. Nadler said he would not negotiate on the hearing's format.
"That's an affair entirely for Congress administration witnesses have to come in and be examined as the committee sees fit," he said.