White House press secretary Sean Spicer has been repeatedly defending President Trump's unproven claims that former president Barack Obama ordered a wiretap on him in 2016. (Bastien Inzaurralde/The Washington Post)

The Republican and Democratic leaders of the Senate Intelligence Committee joined the chorus of lawmakers stating they are not aware of any current evidence supporting President Trump’s claim that his campaign headquarters was wiretapped during the presidential election season.

Committee Chairman Richard Burr (R-N.C.) on Thursday released a joint statement with the ranking Democrat, Sen. Mark R. Warner (Va.), stating that they have not seen data supporting Trump’s claim.

“Based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government either before or after Election Day 2016,” they said.

Burr and Warner are leading the Senate investigation into Russia’s suspected interference in the 2016 elections to aid Trump. They are also examining alleged ties between Trump aides and Russian officials. They were joined last week and again on Wednesday by House Intelligence Committee Chairman Devin Nunes (R-Calif.) — leading a similar investigation in the House — who also stated that he has not seen evidence to support the president’s complaint that his offices were wiretapped during the campaign.

Nunes, who served on Trump’s transition team, declared flatly Wednesday that there was no evidence that Trump Tower was wiretapped while Trump was a candidate.

House Intelligence Committee Chair Devin Nunes (R-Calif.) and Ranking Democrat Adam Schiff (Calif.) expressed doubt, March 15, about President Trump's claim of a 2016 wire tap at Trump Tower. (Reuters)

“I don’t think there was an actual tap of Trump Tower,” Nunes said. He added that if people are taking Trump’s tweets literally — which he advised against — then “clearly the president was wrong.”

House Speaker Paul D. Ryan (R-Wis.) — not for the first time — weighed in on Thursday saying he believes there is no evidence from the intelligence community supporting the idea that Trump was tapped.

“The Intelligence committees in their continuing, widening, ongoing investigation of all things Russia, got to the bottom — at least so far — with respect to our intelligence community that — that no such wiretap existed,” he told reporters.

Trump press secretary Sean Spicer said Thursday that the president stands by his allegation — made in a March 4 tweet — that President Barack Obama ordered surveillance of his phones at Trump Tower in New York in autumn during the campaign.

In a combative exchange with reporters, Spicer was asked whether Trump still believes his claim. “He stands by it,” Spicer said.

Yet Trump admitted Wednesday night in a Fox News interview that he had no solid proof that Obama ordered an effort to monitor his phone calls.

“I’ve been reading about things,” Trump said. The president said that after noticing an article in the New York Times and commentary by Fox anchor Bret Baier, he told himself, “Wait a minute, there’s a lot of wiretapping being talked about.”

In the interview, Trump said that information would soon be revealed that could prove him right, but he would not explain what that information might be. He said he would be “submitting certain things” to a congressional committee and that he was considering speaking about the topic next week.

“I think you’re going to find some very interesting items coming to the forefront over the next two weeks,” Trump said.

Tensions have flared in recent days between lawmakers and the Justice Department on the subject of Russia — especially over FBI Director James B. Comey’s approach to providing Capitol Hill with information about the bureau’s probe into Russia’s activities in the 2016 campaign.

Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) is holding up the confirmation of deputy attorney general nominee Rod J. Rosenstein until Comey testifies before his committee on the scope of the FBI’s Russia probe. And Sens. Lindsey O. Graham (R-S.C.) and Sheldon Whitehouse (D-R.I.), leaders of the Senate Judiciary Committee’s crime and terrorism subcommittee, sent Justice Department officials a letter last week asking for evidence of any wiretapping warrants or applications. Graham threatened Wednesday to subpoena that information.

Grassley became animated in an interview Wednesday in speaking on the subject.

“It doesn’t matter whether you have a Republican or Democrat president, every time they come up here for their nomination hearing . . . I ask them, ‘Are you going to answer phone calls and our letters, and are you going to give us the documents we want?’ And every time we get a real positive ‘yes!’ And then they end up being liars!” Grassley said, yelling into the phone during an interview with The Washington Post.

“It’s not if they’re treating us differently than another committee. It’s if they’re responding at all.”

The tension could break into the open Monday during a House Intelligence Committee public hearing on Russia. The hearing will feature Comey and Adm. Mike Rogers, head of the National Security Agency. It will provide a rare chance for lawmakers to grill the FBI director and other officials in a public setting on the allegations that Russia intervened in the campaign in an attempt to tilt it toward Trump.

Phillip Rucker contributed to this report.