Democrats in the US House of Representatives have decided to launch contempt proceedings against Attorney General William Barr.
They took action after he failed to comply with a House Judiciary Committee subpoena to submit an unredacted version of the Mueller report.
The Department of Justice had previously called the request “premature and unnecessary”.
The Democratic-led committee said the vote will be held on Wednesday.
The attorney general also missed a deadline last week to release an uncensored version of the report.
Democrats also want Mr Mueller to testify before Congress on his findings.
On Sunday, US President Donald Trump said on Twitter that the special counsel should not testify before lawmakers.
The US president had previously said he would not block Mr Mueller from giving evidence to Congress, and leave the final decision to Mr Barr.
The 448-page Mueller report found no collusion between the Trump campaign and Russia during the 2016 election campaign, but did not reach a conclusion on obstruction.
Democrats hope Mr Mueller’s testimony may offer insights into parts of the report currently shrouded by redactions.
“Why would the Democrats in Congress now need Robert Mueller to testify,” Mr Trump tweeted on Sunday.
“There was no crime, except on the other side (incredibly not covered in the report), and no collusion.”
It emerged last week that Mr Mueller had written Mr Barr and expressed frustration that the attorney general’s summary did not capture the full context of the special counsel’s findings.
“[Committee Chairman Jerrold Nadler] has been very patient,” said committee member David Cicilline in an interview with Fox News.
“But the members of our committee need to see the full report and the supporting documents so we can continue to do our work [and] conduct oversight in a sober and responsible way.”
Tension between Mr Barr and congressional Democrats is already high.
Earlier this month, the attorney general refused to testify to the Democratic-led House Judiciary Committee after Democrats insisted he be questioned by a staff lawyer.
Senior Democrats have called on him to resign, while Republicans have argued that Mr Barr is being targeted for political gain.
-BBC
