An administration official will testify on Wednesday that former national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE painted President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE's personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE as a possible obstacle on Ukraine policy, CNN reported.

Christopher Anderson, a former assistant to former special envoy for Ukraine Kurt Volker Kurt VolkerGOP senators request details on Hunter Biden's travel for probe Yovanovitch retires from State Department: reports Live coverage: Senators enter second day of questions in impeachment trial MORE, will reportedly tell the House committees conducting the impeachment inquiry that Bolton warned that Giuliani was intertwined with the president’s decisionmaking on Ukraine.

Anderson will say that Bolton told him that he was seeking more senior White House involvement in Ukraine policy development, according to CNN.

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"However, he cautioned that Mr. Giuliani was a key voice with the President on Ukraine which could be an obstacle to increased White House engagement," Anderson will say in his prepared statement, which CNN obtained.

Anderson served between 2017 and 2019 before Catherine Croft, who is also scheduled to testify Wednesday, took over the position this summer, the network noted. She is expected to provide information on receiving calls from Giuliani allies seeking to influence policy and the meeting during which an “informal hold” was placed on Ukraine military aid, it added.

"The only reason given was that the order came at the direction of the President," she will reportedly say.

Democrats allege Trump held up the aid to pressure Ukraine to help him in his reelection bid.

Both State Department officials are expected to bring context to the evolution of Trump’s Ukraine policy and confirm details from previous testimony, according to CNN.

An attorney representing both Anderson and Croft will reportedly tell the House committees that neither is the whistleblower whose complaint about Trump's dealings with Ukraine sparked the impeachment inquiry.

Neither official was listening in on the July 25 phone call between Trump and the Ukrainian president in which Trump asked Kiev to look into former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and his son, CNN noted.

The White House didn’t immediately return a request for comment from The Hill.

Previous reports indicated Giuliani initiated a pressure campaign to influence Ukraine policy.