Joe Biden called on President Trump on Saturday, Sept. 21, to release a transcript of his phone call with Ukraine's president to see whether he pressured the foreign leader to investigate the former vice president.

Biden, the top polling 2020 Democratic president candidate who bests Trump in every head-to-head match in battleground states and nationwide, said the president would only do that because "he knows I'll beat him like a drum."

Trump and his allies reportedly wanted Ukranian President Volodymyr Zelensky to look into Biden's efforts in 2016 to convince Ukraine to fire its top prosecutor, who at the time was also investigating a natural gas company that employed Biden's son, Hunter. Biden contends that he knew nothing of his son's business dealings and was acting on behalf of the United States, which saw the prosecutor as ineffective at stamping out corruption. No evidence has been found that Biden was operating on behalf of his son.

Biden, campaigning in Des Moines at the Iowa Steak Fry, wouldn't say whether Trump deserves to be impeached over his alleged conversations with Zelensky but said the House needs to investigate it.

"This appears to be an overwhelming abuse of power, to get on the phone with a foreign power who is looking for help from the United States and ask about me, if that's what happened, that's what appears to have happened," Biden told reporters. "Trump's doing this because he knows I will beat him like a drum and is using the abuse of power and every element of the presidency to try and smear."

Trump has neither confirmed or denied that he spoke to Zelensky about Biden, saying only that his conversations with the foreign leader were appropriate and calling these latest allegations another witch hunt against him.

News of the call came to light after an intelligence official whistleblower shared with the intelligence agency's inspector general that the official had heard the president make a promise to a foreign leader that wasn't appropriate. Subsequent reporting has found that the call was with Ukraine and related to Trump's desire to get dirt on his possible political opponent.

However, no one has seen the actual complaint filed by the whistleblower because Congress hasn't been provided a copy.

This article was written by Colby Itkowitz, a reporter for The Washington Post.