"I am writing to urge that the Senate Select Committee on Intelligence, in its inquiry into Russia's interference in the U.S. election, conduct a thorough review of any and all financial relationships between Russia and President Trump and his associates," he wrote.

The Senate Intelligence Committee is currently investigating Russia's meddling in the 2016 White House election, including any potential ties between the Trump campaign and Russia.

Democrats have pressed for months for Trump to turn over his tax returns, suggesting they believe the financial documents could show ties to or significant investments with Russian companies that explain the president's warmer tone toward Russian President Vladimir Putin.

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Wyden noted in his letter that he's formally asked the Senate Finance Committee, where he is the top Democratic member, to request the president's tax returns.

The Oregon lawmaker didn't specifically ask Burr and Warner to include a request of the tax documents as part of the Intelligence Committee's probe, but noted that the investigation "provides an opportunity to immediately address these matters."

"Efforts to understand these relationships and to separate fact from speculation have been hampered by the opacity of the finances of President Trump and his associates," Wyden wrote.

Asked about Wyden's letter during a press conference, Burr pledged that the committee would look "anywhere intelligence suggests that there might have been any type of relationship or efforts to influence U.S. elections."

Warner interjected to say that Trump "should have, and in the best interest of the people, released [his] tax returns."

Wednesday's letter comes after The Associated Press reported last week that Paul Manafort, Trump's former campaign manager, worked a decade ago with a Russian billionaire to advance the interests of Putin’s government.

FBI Director James Comey confirmed earlier this month that the bureau is investigating any ties between Trump officials and Russia, though he declined to say which officials are the focus of their probe.

Trump and the White House have repeatedly dismissed questions about any ties between campaign or administration officials and Putin.

Asked during a press briefing on Tuesday if the White House was trying to "revamp its image" amid the Capitol Hill probes, press secretary Sean Spicer argued that reporters are looking for connections that don't exist.

"If the president puts Russian salad dressing on his salad tonight, somehow that's a Russian connection," he joked.