NEW HAMPTON, Iowa — Joe Biden on Thursday called an Iowa voter a "damn liar" and challenged him to a pushup contest after the man questioned the former vice president's age as well as his son's business dealings in Ukraine.

The man, who said he was an 83-year-old retired farmer, said the 2020 candidate is too old to be president and compared Biden's diplomatic efforts in Ukraine to Trump's.

The man claimed without evidence that Biden had "sent" his son Hunter to Ukraine "to get access to" ex-Ukrainian President Petro Poroshenko.

"You're selling access to the president just like" Trump, the man added.

Biden shot back, "You're a damn liar, man. That's not true and no one has ever said that. No one has proved that."

The man claimed he heard the allegation on MSNBC.

"You don't hear that on MSNBC," Biden said. "You do not hear that at all."

Biden then directed the man's attention to the questions about his age, challenging thim to do pushups, run or take an IQ test with him.

Biden then returned to pushing back on the Ukrainian allegations

"No one has said my son has done anything wrong," he said.

"I didn't say you were doing anything wrong," the voter responded.

"You said I set up my son to work at an oil company," Biden said. "Isn't that what you said? Get your words straight, Jack."

When the man said he wasn't voting for Biden in the state's caucuses on Feb. 3, Biden shot back, "You're too old to vote for me."

Biden also appeared to refer to the man as "fat," though campaign adviser Symone Sanders said that the former VP was saying "facts."

Speaking to NBC News later, the man refused to give his name and said he doesn't consider himself to be a Democrat or Republican but that he hates Trump. However, the man said he would vote for Biden if he becomes the Democratic nominee.

Biden later explained his vehement reaction by saying, "What I wanted to do is shut this down."

He was again asked by a reporter at another campaign stop if he called the man fat.

"No, I didn't," he said.

There is no evidence that Biden acted improperly in handling Ukraine policy while his son was on the board of Burisma, a Ukrainian gas company that was at one time under investigation by the country's then-lead prosecutor, Viktor Shokin.

Biden in 2016 pushed for Shokin's ouster in accordance with the wishes of multiple countries and international bodies, including the European Union and the International Monetary Fund, because of widespread concerns that Shokin was ignoring corruption. The investigation into Burisma was reportedly dormant by the time Biden pushed for Shokin's ouster.

In a July 25 phone call, President Donald Trump asked Ukrainian President Volodymyr Zelenskiy to investigate the Bidens and a debunked conspiracy involving Ukraine and the 2016 election. The Trump administration also placed a hold on nearly $400 million in military aid to Ukraine at roughly the same time.

That phone call led to a CIA analyst detailed to the White House filing a formal whistleblower complaint alleging that Trump was abusing his office to have a foreign country provide him with electoral assistance in 2020. That complaint led to the House impeachment inquiry. Trump released the hold on military aid two days after Congress was first made aware of the complaint's existence.

On Thursday, House Speaker Nancy Pelosi, D-Calif., called on her chairmen to begin drafting articles of impeachment against Trump for those actions.

Mike Memoli reported from Iowa. Allan Smith reported from New York.