Devin Nunes (pictured above), a California Republican and a member of US President Donald Trump's transition team, told ABC News on Tuesday, he would "never reveal those sources" that gave him information on possible Rusian ties to officials in Trump's campaign and administration.

Nunes confirmed that he had met last week on White House grounds with what he called a secret source who he claims showed Trump associates' communications with Russians may have been captured in "incidental" surveillance of foreigners in November, December and January.

Read: Constant information drip deepens Donald Trump's Russian woes

The meeting came a day after FBI Director James Comey had debunked Trump's claim that former President Barack Obama had wiretapped him.

Nunes then said he told Trump about the information he'd allegedly seen. His office later said Nunes did not intend to share the information or its source with other members of his own committee as is typically done by US congressional committee investigations.

Asked on Tuesday by reporters if he would continue leading the investigation, Nunes said, "Why would I not?"

"We're doing a very thorough job on this investigation," he added. "Everything is moving forward as is."

"I'm sure the Democrats do want me to quit," Nunes later told Fox, "because they know that I'm quite effective at getting to the bottom of things."

Democrat Jim Himes of Connecticut told the broadcaster MSNBC's "Morning Joe" program that Nunes has scrapped all meetings and open hearings that were scheduled for this week. "The committee has been put into suspended animation," Himes said.

Canceled hearing questions

A hearing canceled by Nunes last week would have been the first opportunity for the public to hear former Acting Attorney General Sally Yates' account of her role in the firing of Trump's first national security adviser, Michael Flynn, in February.

"The Washington Post" reported this week that the Trump administration sought to block Yates from testifying to Congress in the House investigation of links between Russian officials and Trump's presidential campaign.

The newspaper reported that the Justice Department had notified Yates earlier in March that the administration considered much of the possible testimony to be barred from discussion in a congressional hearing because the topics are covered by the presidential communication privilege.

Yates was fired in January after she refused to defend the administration's first travel ban. She alerted the White House that Flynn had been misleading officials in his account of a December phone call with the Russian ambassador to the United States in which sanctions against Russia were discussed. 

Along with former CIA Director John Brennan and former Director of National Intelligence James Clapper, Yates has agreed to testify publicly before the House intelligence committee.

Democrats smell blood

Democrats decried White House entanglement in the House of Representatives committee's investigation into the election campaign, its aftermath and potential contacts between Trump officials and Russians.

The Senate intelligence committee is doing its own investigation and since late July the FBI has been conducting a counterintelligence investigation into Russia's meddling and possible coordination with the Trump campaign.

Virginia Senator Mark Warner, the senior Democrat on the Senate's Intelligence Committee, said that White House meddling is not helping to "remove the cloud that increasingly is getting darker over the administration." Democratic members of Nunes' House committee said his ability to lead a bipartisan probe has been fatally compromised.

One member of the committee, Democrat Adam Schiff said, "We've reached the point, after the events of this week, where it would be very difficult to maintain the credibility of the investigation if the chairman did not recuse himself from matters involving either the Trump campaign or the Trump transition team of which he was a member."

Democrats argued Nunes' loyalty to Trump is greater than his commitment to leading an independent investigation.

White House denials

The White House on Tuesday again denied it had tried to hobble Yates' testimony. Trump's spokesman, Sean Spicer claimed that reporters were seeing conspiracies where none exist. "If the president puts Russian salad dressing on his salad tonight, somehow that's a Russian connection," he suggested.

Trump tweeted on Monday that instead of probing his associates, the committee should be investigating his Democrat opponent Hillary Clinton's ties to the Kremlin. 

House Speaker Paul Ryan reiterated his support for Nunes and Nunes himself said all of the controversy was standard for Washington. "It's the same thing as always around this place - a lot of politics, people get heated, but I'm not going to involve myself with that," he said.

Republicans' reputations on the line

"I think there needs to be a lot of explaining to do," said Senator John McCain.

"I've been around for quite a while and I've never heard of any such thing. And - obviously - in a committee like an intelligence committee, you've got to have bipartisanship, otherwise, the committee loses credibility. There's so much out there that needs to be explained by the chairman," he said.

Trump's approval ratings have fallen and those supporting an independent commission are rising. In the latest Quinnipiac poll, 66 percent of voters favor an independent inquest.

jbh/sms (Reuters, AP)