House Judiciary Committee Chairman Jerry Nadler, D-N.Y., cast doubt on whether special counsel Robert Mueller will appear before the panel later this month.

“Well, now that the president has said what he’s said, I am less confident than I was,” Nadler said during an interview with CNN’s Alisyn Camerota on Wednesday. The committee tentatively pitched having Mueller appear before them on May 15, but nothing was finalized.

Over the weekend, President Trump said that he opposes permitting Mueller to appear before lawmakers.“Bob Mueller should not testify,” Trump tweeted on Sunday. “No redos for the Dems!”

Nadler said he expects Trump will try to prevent Mueller from appearing, but said he was uncertain whether Trump’s attempts would be successful.

“I think the president will try to stop Robert Mueller, whether he’ll succeed is another question” Nadler said. “The president is taking as I’ve said an absolutely lawless attitude that he wants to deny the American people and the Congress all information about his own wrongdoing, about his own breaking the law.”

“For him to come out and say that he’s going to oppose all subpoenas, that’s a direct challenge to having a Congress that can function,” Nadler said, adding that it signaled Trump wanted to be a “monarch.”

[Read more: Barr bucks Trump, backs Mueller testimony: Report]

Mueller concluded his investigation in Russia and did not conclude that there was sufficient evidence that there was a criminal conspiracy between the Trump campaign and the Kremlin during the 2016 election. However, Mueller did not make a determination on obstruction of justice.

Attorney General William Barr said there was not sufficient evidence to prove an obstruction crime, prompting Democrats to claims that Congress must investigate and decide.

Later Wednesday, the House Judiciary Committee will vote on whether to hold Barr in contempt of Congress for not complying with a subpoena, despite a warning from the Justice Department that it will “be compelled to request that the president invoke executive privilege” regarding Mueller’s report and the underlying evidence.