WASHINGTON (Reuters) – President Donald Trump’s oldest son, Donald Trump Jr., on Thursday will testify privately to the Senate Judiciary Committee, which is looking into allegations of Russian interference in the 2016 U.S. election, Senate aides said on Wednesday.

Trump Jr. had been invited to testify in public in a hearing in July, but reached an agreement to speak privately with committee staff.

“We look forward to a professional and productive meeting and appreciate the opportunity to assist the committee,” Alan Futerfas, a lawyer for Trump Jr., said in a statement.

Russia has loomed large over the first six months of the Trump presidency. U.S. intelligence agencies have concluded that Russia worked to tilt last year’s presidential election in Trump’s favor.

Special Counsel Robert Mueller is leading an investigation, which is also examining potential collusion with Russia by the Trump campaign. Several congressional committees are also looking into the matter.

Moscow has denied any meddling. Trump denies any collusion by his campaign, while regularly denouncing the investigations as political witch hunts.