Deputy Assistant Secretary of State George Kent reportedly raised concerns earlier this year about what he described as pressure from President TrumpDonald TrumpOvernight Defense & National Security — The Pentagon's deadly mistake Overnight Energy & Environment — Presented by Climate Power — Interior returns BLM HQ to Washington France pulls ambassadors to US, Australia in protest of submarine deal MORE and his lawyer Rudy GiulianiRudy GiulianiRoger Stone served with Capitol riot lawsuit during radio interview FEC finds Twitter didn't break law by blocking spread of Hunter Biden story Juan Williams: The toxic legacy of Trump's corruption MORE to investigate Trump's political opponents.
Sources told The New York Times that Kent, who oversees Ukraine policy, expressed concern as far back as March about Giuliani's role in a "disinformation" campaign that aimed to smear people including former Vice President Joe BidenJoe BidenHouse Democrat threatens to vote against party's spending bill if HBCUs don't get more federal aid Overnight Defense & National Security — The Pentagon's deadly mistake Haitians stuck in Texas extend Biden's immigration woes MORE and then-U.S. Ambassador to Ukraine Marie Yovanovitch.
Kent was deposed on Tuesday as part of the House Democrats' impeachment inquiry.
Democrats are investigating the president following revelations that he pushed Ukraine to investigate the Bidens.
The whistleblower's complaint alleges that White House officials believed Trump was using his office for a political gain during a July 25 call where he pressured Ukraine's leader to investigate Biden, and that officials sought to cover up the call.
Kent's testimony on Tuesday follows last week's testimony from Yovanovitch, who was recalled from her post in May, and former White House aide Fiona Hill.
Olivia Beavers contributed to this story.