Former FBI Director James Comey will speak privately with Robert Mueller, special prosecutor in the Russia probe, prior to testifying in public before the House or the Senate.
House Oversight Committee Jason Chaffetz, R-Utah, said that decision of Comey's means he would delay a hearing he had planned for this week.
"Spoke with Comey. He wants to speak with special counsel prior to public testimony. Hearing Wed postponed," Chaffetz tweeted. Comey was also slated to talk to the Senate Intelligence Committee.
Mueller, a former FBI chief, was appointed to the job by the Justice Department last week, about a week after Trump abruptly fired Comey.
The Justice Department informed President Trump of its decision to appoint a special counselor shortly before announcing it. Trump said he looked forward to a "thorough investigation."
"As I have stated many times, a thorough investigation will confirm what we already know — there was no collusion between my campaign and any foreign entity," Trump said last week.
Democrats, in particular, have demanded an independent investigation into Russia's interference in last year's presidential election, even after Senate and House committees launched separate probes into the matter.
Mueller served as FBI director for 12 years under former Presidents George W. Bush and Barack Obama.
The probe into Russia could last a few months to a couple years. Mueller's first course of business will be submitting a budget for his investigation within 60 days of his appointment.