FILE - Special Counsel Robert Mueller in Washington.
FILE - Special Counsel Robert Mueller in Washington.

President Donald Trump fired new taunts Monday at opposition Democrats in the ongoing fight to shape the narrative of special counsel Robert Mueller's investigation and report on Russian meddling in the 2016 presidential election.

In a Twitter comment, Trump sarcastically said, "Bob Mueller was a great HERO to the Radical Left Democrats" while his 22-month investigation was underway.

But Trump said when Mueller concluded that he and his campaign did not collude with Russia to help him win the White House and that "our highly respected" Attorney General William Barr decided obstruction of justice charges were not warranted, "the Dems are going around saying, “Bob who? Sorry, don’t know the man.” He provided no examples of this.

President Donald Trump arrives at a rally at Resch
President Donald Trump arrives at a rally at Resch Center Complex in Green Bay, Wis., Saturday, April 27, 2019.

Barr is set to testify before a Senate committee Wednesday about his no-obstruction decision and his oversight of the end of the Mueller probe. But Barr's planned appearance before the House Judiciary Committee Thursday is in doubt in a dispute over who will question him.

Committee chairman Jerrold Nadler of New York wants to give the 41 committee members five minutes each to ask Barr questions and then another 30 minutes for both Democratic and Republican lawyers for the committee to make more inquiries of Barr.

Barr has agreed to questioning by the House lawmakers, but balked at the further questioning by the lawyers. The Justice Department has told the House committee Barr may not show up.

Nadler says Barr has no choice.

House Judiciary Committee Chair Jerrold Nadler, D-
House Judiciary Committee Chair Jerrold Nadler, D-N.Y., speaks with a reporter as he departs a news conference after the House voted to reauthorize the Violence Against Women Act, April 4, 2019, on Capitol Hill in Washington.

"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 are procedures for questioning him are," Nadler said Monday.

He added that the committee will take "whatever action we have to take" if Barr skips out on the questioning.

White House press secretary Sarah Sanders said the Trump administration cooperated with Mueller's investigation, but derided the House panel's demand for questioning of Barr by committee lawyers.

"You have to look at the outrageous behavior, particularly of the House Democrats, who are asking for things they know they can't have, that they know they have no legal authority to have, and frankly they're just acting really childish," Sanders said. "It's almost embarrassing to the House Democrats the way that they're behaving."

FILE - U.S. Attorney General William Barr departs
FILE - U.S. Attorney General William Barr departs after speaking at a news conference to discuss Special Counsel Robert Mueller's report on Russian interference in the 2016 U.S. presidential race, in Washington, April 18, 2019.

Mueller cited 11 instances of possible obstruction of the investigation by Trump, saying that "while this report does not conclude that the president committed a crime, it also does not exonerate him."

With Mueller not reaching a decision on the obstruction question, Barr said he concluded no criminal charges against Trump were warranted.

Democrats say they want to question Barr how he reached his no-obstruction decision.

WATCH: Trump subpoenas