Sen. Lindsey Graham wants to investigate President Donald Trump's business dealings with Russia
Sen. Lindsey Graham - (CNN screen grab)

Sen. Lindsey Graham (R-SC) wants to open a congressional investigation of President Donald Trump's business dealings.

The Republican chairman of the Senate Judiciary Committee was intrigued by James Clapper's refusal to answer a question about the president's business dealings with Russia, which the former director of national intelligence suggested could jeopardize an ongoing investigation, reported CNN.

Graham asked Clapper if he had any concerns about Trump's business ties with Russia when the intelligence committee put together an assessment, and the former official said he had not at that time.

But Clapper declined to comment, citing a possible investigation, when Graham broadened the time frame in a follow-up question.

Graham told CNN's Manu Raju that he would first see how the FBI was conducting its own investigation of the president's foreign business dealings before launching a congressional probe, which would be overseen by the committee he chairs.

The senator is interested in seeing Trump's tax returns, which he has refused to release, but Graham said he's not yet ready to call for a subpoena.