Updated March 16, 6:30 p.m. ET
The Republican and Democrat leading the Senate investigation into Russian meddling in the 2016 presidential election appeared Thursday to counter White House claims that there may have been surveillance of some sort on Trump Tower around the campaign, even if there was not specific wiretapping as President Trump said in a tweet nearly two weeks ago. Meanwhile, the White House aggressively defended the president's assertions on Thursday.
"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," Sen. Richard Burr, R-N.C., and Sen. Mark Warner, D-Va., said in a joint statement.
The White House has asserted in recent days that when Trump tweeted that "Obama had my 'wires tapped' in Trump Tower," he was referring to various surveillance measures available to the U.S. government.
In a Fox News interview on Wednesday night, Trump said that "wiretap covers a lot of different things." He also said in the interview that he expects "some very interesting items coming to the forefront over the next two weeks."
White House press secretary Sean Spicer reacted heatedly when asked about the statement from the intelligence committee on Thursday afternoon, accusing the media of covering the Russia investigation in a biased manner.
Spicer said the president "stands by" his claim, then went on to read off a number of media reports, many of which revolved around the investigation of possible Russian interference in the campaign but not necessarily surveillance of Trump Tower.
The response from Spicer lasted approximately nine minutes and involved the press secretary repeating the accusation of possible links between the Trump campaign and Russia, which the intelligence committees have not said they have evidence to support.
Spicer also repeated an accusation from a report on Fox News, based on anonymous sources, that then-President Barack Obama used British intelligence to spy on Trump during the campaign.
House Intelligence Committee Chairman Devin Nunes said on Wednesday he doesn't believe "there was an actual tap of Trump Tower," but the statement from the Senate intelligence leaders represents broader pushback.
Asked Thursday to weigh in on wiretapping, House Speaker Paul Ryan said, "We've cleared that up. That — that we've seen no evidence of that."
Trump has not produced any evidence to back his assertion. Spicer said this week, "I think there is significant reporting about surveillance techniques that have existed throughout the 2016 election." And, referring to the president, "I think he feels very confident that what will ultimately come of this will vindicate him."
The top Democrat on the House committee, Adam Schiff, told NPR's All Things Considered on Wednesday "there's no evidence" to support Trump's claim. Schiff says the question will remain: "Why would the president do this? And that's a question the president will have to answer."
Speaking at a Capitol Hill news conference on Wednesday, Nunes, a Republican from California, said:
FBI Director James Comey is likely to face questions about whether the agency obtained a warrant to wiretap Trump Tower at a House committee hearing on March 20. Nunes and Schiff confirmed NSA Director Mike Rogers will appear along with Comey at the hearing.
Sen. Lindsey Graham of South Carolina, chairman of a Senate judiciary subcommittee investigating Russia, is also expecting some answers. In an interview on NBC's Today show, Graham threatened to subpoena the Department of Justice to force officials to reveal whether they have been investigating the Trump campaign.
Graham said the Senate will also hold up the nomination of Rod Rosenstein, Trump's pick for deputy attorney general, until Congress is provided with information "to finally clear the air as to whether there was ever a warrant issued against the Trump campaign."
Graham and Sen. Sheldon Whitehouse, the subcommittee's ranking Democrat, sent a letter to Comey two weeks ago asking him to provide the information by Wednesday.
The former president's office has denied the charge. Former Director of National Intelligence James Clapper has said he knew of no warrant to wiretap Trump.
Graham says he knows of no evidence of such a warrant but added that he is now "getting concerned, because it's taking so long to answer my letter." The House Intelligence Committee had asked the Department of Justice to provide evidence backing up the president's claim by March 13. Nunes and Schiff now say they expect an answer by March 20.
Intelligence officials have concluded that Russia employed cyberattacks during the presidential campaign intended to hurt Hillary Clinton and aid Trump.
Nunes said it is possible that conversations Trump campaign officials had with Russia were captured in surveillance of Russian officials, such as contact between former national security adviser Michael Flynn and Russia's ambassador to the U.S. Nunes expressed concern that such surveillance was leaked for political motivation and is asking for more information on such surveillance from the intelligence community.