Trump has provided no evidence to back the explosive claim, and a spokesperson for Obama has denied that the former president ordered a tap. The White House has asked the congressional intelligence committees to investigate Trump's allegation.

Two senators have asked the Department of Justice and FBI for any information they have related to President Donald Trump 's accusation that President Barack Obama wiretapped him ahead of the 2016 election.

In a letter Wednesday, Sens. Lindsey Graham, R-S.C., and Sheldon Whitehouse, D-R.I., requested that the Justice Department "provide us copies of any warrant applications or court orders ... related to wiretaps" of Trump, his campaign or Trump Tower. The senators serve on the Senate Judiciary Committee's Subcommittee on Crime and Terrorism, which has oversight of the Justice Department's criminal division.

"As chairman and ranking member of the Senate Judiciary Committee's Subcommittee on Crime and Terrorism, we would take any abuse of wiretapping authorities for political purposes very seriously. We would be equally alarmed to learn that a court found enough evidence of criminal activity or contact with a foreign power to legally authorize a wiretap of President Trump, the Trump campaign, or Trump Tower," the senators wrote in a letter to Acting Deputy Attorney General Dana Boente and FBI Director James Comey.

Trump on Saturday accused Obama of tapping his phones "during the very sacred election process." He compared it to President Richard Nixon and the Watergate scandal.

Since then, though, Trump aides have not pointed to any specific evidence to back his claim. Comey reportedly asked the Justice Department to publicly reject the assertion, while the chairmen of both the House and Senate intelligence committees have said they have not seen evidence to support it.

In the letter, Graham and Whitehouse emphasized that they sought documents "redacted as necessary to protect intelligence sources and method that may be compromised by disclosure and to protect any ongoing investigations." Later Wednesday, Graham told MSNBC that he would subpoena for the information if officials do not provide it.