The former New York City mayor sat with NPR’s Steve Inskeep for an interview that aired Tuesday. Giuliani spoke about the Senate trial regarding the president’s attempts to withhold military aid to Ukraine in exchange for the country’s announcement of an investigation into the former vice president and his son Hunter Biden.

“Biden should be investigated” after the trial ends, “100%,” Giuliani told Inskeep. “I would have no problem with him doing it. In fact, I would have a problem with him not doing it. I think he would be saying that Joe Biden can get away with selling out the United States, making us a fool in the Ukraine.”

"Absolutely; 100%," Giuliani told @NPRinskeep. “I would have no problem with [Trump] doing it. In fact, I'd have a problem with him not doing it. I think he would be saying that Joe Biden can get away with selling out the United States, making us a fool in the Ukraine." — Katherine Faulders (@KFaulders) February 4, 2020

Giuliani was central in the events that led up to the House conducting an inquiry that resulted in Trump’s impeachment in December. The president’s personal attorney conducted shadow diplomacy for Trump with Ukrainian officials to get them to announce an investigation into the Bidens, the younger who served on the board of Ukrainian gas company Burisma while his father ― who is now one of Trump’s 2020 rivals ― served as vice president of the United States. Trump is accused of withholding congressionally approved U.S. military aid to Ukraine while pushing for the country’s president to announce the investigation.

“He’s the chief law enforcement officer of the United States. He certainly shouldn’t back away from it,” Giuliani said of Trump investigating Biden. Technically, the U.S. attorney general is the chief law enforcement officer, serving in the executive branch under the president.

Giuliani told Inskeep that he’s still looking into the Bidens’ relationship with Ukraine, despite there being no evidence of wrongdoing by the Bidens. Asked if he’s investigating Biden on the president’s orders, Giuliani said, “He hasn’t told me not to do it.”

The attorney’s comments to NPR come as the Senate prepares for a vote in the impeachment trial Wednesday that will likely end in the president’s acquittal. All 53 Republican senators are expected to vote against convicting Trump on the charges ― abuse of power and obstruction of Congress ― after almost all refused to allow witnesses in the trial.

Some senators, such as Lamar Alexander (R-Tenn.) and Susan Collins (R-Maine), expressed disappointment with Trump’s actions and said it was inappropriate to ask a foreign leader to investigate a political opponent. But both lawmakers still plan to acquit the president, with Collins saying Tuesday that she believes Trump “has learned from this case” and “will be much more cautious in the future.”

Susan Collins, in saying she won’t vote to remove Trump, says he learned a lesson. Trump has repeatedly said he behaved perfectly and did nothing wrong. — Josh Dawsey (@jdawsey1) February 4, 2020

But Giuliani’s remarks Tuesday signify otherwise: “I believe that it would be one of the great corrupt events in American history if this case is not investigated at the highest levels of two governments.”