Amid growing calls for his recusal from the investigation of Russian meddling in the election, and revelations that raise questions about his partisanship, House Intelligence Chairman Devin Nunes is digging in his heels.

"Why would I not?" the California Republican told reporters when asked whether he would continue to lead the Russian probe. "That sounds like their problem," he said of Democrats, including Ranking Member Adam Schiff, who argue the chairman's proximity to the Trump administration as a member of the transition team, his recent briefing of a president whose associates are under investigation, and his refusal to share information with his colleagues has compromised the committee's work and are thus grounds for his recusal.

The controversy surrounding the chairman of the committee, which handles the nation's most highly classified information, has brought the panel's work to a standstill. Key public hearings along with regular committee activity have been canceled. Calls by Democrats for an independent commission have grown, as have partisan rifts.

The stalling on the House side shifts the spotlight to the Senate Intelligence Committee, which figures to take the lead in the congressional probe of Russian meddling.

Chairman Richard Burr and Ranking Member Mark Warner will host a joint press conference on Wednesday afternoon to address the foreign interference in the 2016 election. Members of the Senate committee plan to question President Trump's son-in-law, Jared Kushner, who now works in the White House, about meetings he arranged with Russians during the transition.

Sen. Warner, a Democrat of Virginia, told reporters he would like the committee to ask former Acting Attorney General Sally Yates to testify, after the House intelligence chairman postponed her scheduled appearance Tuesday. “Clearly, she is an individual that we’re going to want to talk to as well," he said.

In a press briefing Tuesday, White House Press Secretary Sean Spicer vigorously refuted a Washington Post story suggesting the administration had reason to want Yates not to testify, and that Nunes canceled the hearing to shield the White House from having to invoke executive privilege to keep her from doing so.

"I hope she testifies. I look forward to it," Spicer said. "We have no problem with her testifying. Plain and simple."

Previously, Yates had alerted the White House counsel of contacts between former adviser Michael Flynn and the Russian ambassador. The Post report that the administration tried to block her from appearing before the House panel this week is “false,” Spicer said. Former Director of National Intelligence James Clapper and former CIA Director John Brennan were also scheduled to appear.

Yates, a holdover from the Obama administration, was fired by Trump earlier this year after she refused to enforce his executive order travel ban, which was later challenged in court. Since then, she has been hailed by Democrats, and party operatives in her home state of Georgia have floated her as a possible gubernatorial candidate.

On Friday, Nunes said he postponed the hearing so that FBI Director James Comey, who testified last week that his agency was investigating alleged collusion, and National Security Agency Director Michael Rogers could answer further questions from the committee. But that appearance has not taken place, and the chairman's office said the arrangements have not yet been worked out.

The flap over Yates comes amid news that Nunes had met with a source at the White House the day before he made the unprecedented move of alerting the president that his communications may have been collected in incidental, legal surveillance. Nunes spoke with the press, House Speaker Paul Ryan, and the president before briefing members of his own committee. The move set off a firestorm within the panel, and exposed a rare rift between its leaders.

Nunes has declined to reveal his White House source to members of his committee and said Tuesday that he doesn't plan to do so. The chairman told Bloomberg View that his source was a member of the Intelligence Committee and not a White House staffer. Senate Armed Services Chairman John McCain said in an interview with CBS that Nunes should reveal his source. “I think there needs to be a lot of explaining,” he said.

House Republicans on the committee have come to Nunes' defense, and Ryan has voiced his support for the chairman.

Republicans on the panel say Democrats are the ones waging a partisan war against Nunes. "Jesus would not be a satisfactory chairperson to some of my Democratic colleagues," South Carolina Rep. Trey Gowdy told The Weekly Standard. "They would complain about his hair."

Democrats on the panel say Nunes has undermined the investigation. On Monday, Schiff called for the chairman to step down from the Russia investigation. "I believe the public cannot have the necessary confidence that matters involving the President's campaign or transition team can be objectively investigated or overseen by the Chairman," he said in a statement.

Still, Democrats aren't ready to abandon the committee and want to have a voice in the process. Democratic Rep. Jim Himes said members would only walk away if the chairman prevented them from witness interviews.

Meanwhile, some Senate Republicans are voicing their own concerns about Nunes' behavior and the impact it could have on congressional oversight. In an interview with the "Today" show, Sen. Lindsey Graham said Nunes should explain his White House visit to his committee colleagues. "The House is off track and probably can't get back on track," he said.

White House Correspondent Alexis Simendinger and Congressional Correspondent James Arkin contributed to this report.