WASHINGTON — Tensions are rising between congressional Republicans and President Trump over probes into Russia’s role in the election and claims that Trump Tower was wiretapped.

Senate Judiciary Committee Chairman Charles Grassley, R-Iowa, whose committee is one of several where investigations are fully underway, accused Justice Department officials Wednesday of lying when they promised to share information about ongoing department probes on Russia with lawmakers conducting oversight.

“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, screaming 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.”

Grassley spoke as he awaited a meeting with FBI Director James Comey to determine whether the bureau is investigating alleged Russia interference in last year’s elections. Grassley has threatened to block the nomination of Rod Rosenstein as deputy attorney general until his committee receives an FBI briefing. Late Wednesday afternoon, his committee’s ranking Democrat, Dianne Feinstein, D-Calif. – who also attended the private briefing with Comey – credited Grassley’s “tough language” and the “strength” of his written warnings to the Justice Department for getting the briefing to happen.

Grassley is not alone in voicing frustration at how the administration is interacting with lawmakers trying to investigate allegations of links between the Trump team and Russia. Several key lawmakers are threatening to subpoena the administration for evidence backing up President Trump’s charges that the Obama administration wiretapped his phones during the campaign.

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.

Meanwhile, House Intelligence Committee leaders Devin Nunes, R-Calif., and Adam Schiff, D-Calif., said Wednesday they were prepared to subpoena the Justice Department for evidence to back up Trump’s wiretap claim if the administration does not meet a Monday deadline.

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.

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

But Trump is defending the explosive charge, arguing during an interview with Fox News on Wednesday night that the term “wiretap covers a lot of different things.”

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

Trump’s wiretapping claims, first made on Twitter, were a pivotal episode for many Republican lawmakers, who are losing patience with the president and his administration as they await proof that few believe exists.

Sens. Lindsey Graham, R-S.C., and Sheldon Whitehouse, D-R.I., leaders of the Senate Judiciary Committee’s crime and terrorism subcommittee, also sent Justice Department officials a letter last week asking for evidence of any wiretapping warrants or applications. Graham threatened Wednesday to subpoena that information until he heard that Comey would soon brief them privately on the subject. It was not clear when that briefing would happen – or whether it will satisfy senators threatening to block Rosenstein’s nomination until they receive more information.

Delaying Rosenstein from starting his job could end up hurting those looking to get to the bottom of allegations about Russia. Attorney General Jeff Sessions, a close Trump ally who served as a campaign adviser, has recused himself from investigating anything related to the president – meaning it would fall to the deputy attorney general to take charge of such inquiries, and determine whether to appoint a special prosecutor for the case.

As lawmakers begin to dig into their investigations related to Russia, the rhetoric between them – including many Republicans – and the Trump administration has become more charged.

Nunes and Schiff complained Wednesday that their investigation was being slowed by the Office of the Director of National Intelligence, which has not supplied committee members and staffers with a computer to use while they review documents – forcing them to take notes by hand.

“This has become a bit of a stumbling block for our investigators to actually be able to compile and get through the information,” Nunes said.

“We feel a real sense of urgency about conducting this investigation not only thoroughly but as swiftly as possible,” Schiff said. “So anything that slows us down is a problem.”

An ODNI spokesman said Wednesday that the intelligence community was working “to address the logistical challenges inherent in protecting the security of sensitive intelligence sources and methods.”

Nunes and Schiff also sent Comey, Rogers and CIA Director Mike Pompeo a letter Wednesday demanding a complete list of people whose names have been “unmasked” after popping up in other surveillance – the way, they noted, authorities discovered that former national security adviser Michael Flynn had contacts with Russian Ambassador Sergey Kislyak. If that information isn’t provided by Friday, Nunes said he would likely subpoena those records.

Nunes added that it was a possibility that Trump’s name could appear on such a list. He maintained, however, that he has seen no evidence of improper contact between the president or his affiliates and Russian officials – a conclusion Schiff declined to endorse.

In the course of their investigation, Nunes and Schiff have had fairly regular access to Comey as members of the Gang of Eight, the group of senior lawmakers who receive the highest-level intelligence briefings. House Intelligence Committee members were recently cleared to receive access to the same intelligence as the Gang of Eight; the Senate Intelligence Committee has received briefings from Comey as well.

But in the Judiciary Committee, Comey’s attention has been late in coming, and promises of briefings materialized only after Grassley and Graham threatened to hold up Rosenstein’s nomination.

“That seems to have gotten their attention,” Grassley said during the interview.

Grassley and Graham stress that there are pragmatic reasons for them to be resorting to such measures to get a briefing.

“If there is a criminal investigation regarding the Trump campaign and ties to Russia, I want to know about it because we’re doing congressional investigations of all things Russia,” Graham said in an interview. “I don’t want to run into a criminal investigation not knowing it’s out there.”

For several weeks, the Senate Judiciary panel has asked the FBI for additional information and briefings on allegations of links between the Trump administration and the Kremlin, reiterating the request when Flynn resigned and when Trump made his wiretapping allegations. Grassley said Comey has told him he was awaiting “clearance” to update his committee, even as he made trips to Capitol Hill to huddle with Intelligence Committee members.

Grassley said he’s unsure how Republican colleagues feel about Comey’s reluctance to explain the FBI’s ongoing investigations, but he added: “I imagine a lot of them are much more frustrated than I’ve just demonstrated to you.”