Story highlights "Congress is going to flex its muscles," Graham said

Trump accused Obama of wiretapping the Trump Tower phones

(CNN) Sen. Lindsey Graham said Wednesday he'll subpoena information from the FBI over President Donald Trump's wiretapping allegations if bureau Director James Comey does not provide information about whether there is any validity to the President's claims.

Earlier this month, Trump alleged -- without providing evidence -- that Obama ordered his phones to be wiretapped at Trump Tower during the campaign. Graham and Sen. Sheldon Whitehouse, D-Rhode Island, both asked the Justice Department last week to provide any evidence that would support Trump's claims.

"We wrote a letter -- Sen. Whitehouse and myself -- wanting to know if there's evidence of a warrant issued by the Trump campaign," the South Carolina Republican told CNN's Chris Cuomo on "New Day." "He hasn't answered that letter or confirmed if there's a real investigation of the Trump campaign."

"He needs to answer the letter and give the nation some information about what's going on here," he added.

If the FBI does not provide the information, Graham said he and other senators may subpoena it.

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