NATIONWIDE — More witnesses are set to testify Friday and early next week in public hearings in the impeachment inquiry into President Donald Trump. 

Congress heard from former U.S. Ambassador to the Ukraine Marie Yovanovitch. 

Yovanovitch was ousted from her ambassadorship earlier this year because of what she testified were "unfounded and false claims by people with clearly questionable motives," she said back in October of this year.

Yovanovitch told lawmakers she requested the State Department speak up and defend her amid the alleged smear campaign by Rudy Giuliani and his associates, but her requests went unanswered. 

At its core, the impeachment inquiry concerns Trump's July phone call with Ukrainian President Volodymyr Zelenskiy that first came to attention when an anonymous government whistleblower filed a complaint.

In the phone conversation, Trump asked for a "favor," according to an account provided by the White House. He wanted an investigation of Democrats and 2020 rival Joe Biden. Later it was revealed that the administration was also withholding military aid from Ukraine.

Republicans argue the money was given to Ukraine without any investigation and there was no quid pro quo.

Earlier this week during Wednesday's hearing, William Taylor, the top diplomat who replaced Yovanovitch in Ukraine testified that another State Department witness overheard Trump asking about "the investigations" the day after his phone call with Kyiv.

During the first day of testimony, Taylor and another seasoned foreign service officer, George Kent, the deputy assistant secretary of State, delivered somber accounts about recent months.

They testified in defense of Yovanovitch amid what Kent called Giuliani's "smear" campaign against her; about the dangers of abandoning Ukraine as it faces Russia; and of what Taylor called an "irregular channel" of foreign policy orchestrated by the president's lawyer and carried out by other Trump allies.

Next week Special Advisor to Vice President Mike Pence Jennifer Williams, Director for European Affairs National Security Council Lt. Col. Alexander Vindman, former U.S. Special Envoy to Ukraine Kurt Volker, and former U.S. National security advisor Tim Morrison will testify on Tuesday. 

On Wednesday, the nation is expecting testimony from Ambassador Gordon Sandland, Deputy Assistant Secretary of Defense Laura Cooper, and Undersecretary of State for Political Affairs David Hale. 

LIVE UPDATES: Diplomats Publicly Questioned in Trump's Impeachment Inquiry

The Associated Press contributed to this story.