In a letter sent to Whitaker, Nadler said he will call him in for a formal deposition if he isn't able to reach a "reasonable accommodation" with the Justice Department on additional answers. Nadler said he has asked his staff to work with Whitaker's staff, and "we are available to meet in the coming days for that purpose."
It's unclear if Whitaker would return to Capitol Hill to clarify his answers. A Justice Department spokeswoman declined to comment. The letter comes as Whitaker could have less than a day left in office. The Senate is expected to hold a confirmation vote on President Donald Trump's permanent pick for attorney general, William Barr, on Thursday.
Nadler said Whitaker didn't offer clear responses about his communications with the White House and was inconsistent in testifying about the department's policy on discussing ongoing investigations. In one instance, Nadler pointed to Whitaker's answers to questions about whether Trump "lashed out" at him after Trump's former personal lawyer, Michael Cohen, pleaded guilty to lying to Congress and campaign finance violations. News reports said Trump did lash out at Whitaker, but Whitaker said he did not.
Nadler said the committee "has identified several individuals with direct knowledge of the phone calls you denied receiving" from the White House. "As a result, we require your clarification on this point without delay," Nadler wrote.
He said Whitaker was also inconsistent on whether he had discussed special counsel Robert Mueller's Russia investigation with the president, or with anyone at the White House or in Trump's circle, before Whitaker worked at the Justice Department. He said he did not, but also noted he had interviewed to be a White House counsel dealing with the Russia probe.
Nadler said that claim was made "somewhat incredulously."