WASHINGTON — Former Vice President Joe Biden said Wednesday that he is opposed to testifying in the Senate impeachment trial in exchange for securing testimony from several key witnesses sought by Democrats because he doesn’t want to participate in "some kind of political theater."

The 2020 presidential contender made the comment on the campaign trail in Iowa as the first day of opening arguments in the trial unfolded on Capitol Hill. There have been weeks of debate over whether Democrats should engage in a witness trade deal with Republicans.

Biden on Wednesday was asked if he would call the Republicans' bluff and state that he’d testify if witnesses sought by Democrats go first.

As part of an extended answer in which he defended his son Hunter Biden, whose work in Ukraine is at the center of the impeachment saga, Biden suggested that he opposes such a scenario.

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"The reason why I would not make the deal — the bottom line is this is a constitutional issue. And we're not going to turn it into a farce, into some kind of political theater," Biden said.

"They are trying to turn it into political theater," he added. "But I want no part of being any part of that. And I have no problem, as you'll find out the rest of this campaign, debating Trump, debating the majority leader, debating Lindsey Graham, debating any of these guys. I don't have any problem."

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Biden did not say on Wednesday whether or not he would comply with a Senate subpoena for his testimony.

His remarks came after Senate Minority Leader Chuck Schumer, D-N.Y., said Wednesday during a brief recess from the trial that a witness trade, where Democrats agree to call people like the Bidens so that Republicans agree to hear from people like former national security adviser John Bolton, is "off the table."

There’s no guarantee that the trial will even make it to a witness and documents stage. The resolution adopted by the Senate Tuesday that laid out the initial parameters of the trial said that the Senate would have to vote to allow witnesses and documents later on. Republicans have been largely opposed to incorporating such testimony and records, but Democrats could secure them if they win over four Senate Republicans to vote with them as they need only 51 votes to make it that far.

House Intelligence Committee Chairman Adam Schiff, D-Calif., who is serving as the lead prosecutor in the trial, told reporters on Wednesday that testimony from the Bidens would be "irrelevant and immaterial" to the trial.

"This isn’t like some fantasy football trade as I said yesterday. This isn’t we'll offer you this if you give us that. We'll offer you a witness that is irrelevant and immaterial, who has no relevant testimony but a witness that will allow us to smear a presidential candidate if you want to get a legitimate witness."

In an interview on MSNBC Wednesday, Sen. Richard Blumenthal, D-Conn., said that there were ongoing talks about witnesses and said Democrats won’t have that negotiation publicly.

"We have sought four witnesses that have direct firsthand knowledge: John Bolton who was in the room with the president trying to talk him out of this so-called drug deal, Mick Mulvaney who took the order and began to execute it with Robert Blair and Michael Duffy. These witnesses have relevant knowledge; Hunter Biden has none."

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Sen. Bernie Sanders, I-Vt., said that he would not be in favor of a witness trade that would lead to the testimony of either of the Bidens.

"That issue has nothing to do with the impeachment trial," Sanders said. “Trump is being charged with abuse of power and obstruction of justice. Those are the issues. Those are the witnesses that need to be called and that's the kind of debate that needs to happen."

Sen. Chris Coons, D-Del., a longtime friend of the former vice president, said Tuesday that if it came down to Joe Biden testifying, he would be able to handle it.

"I can't imagine a person more comfortable in the well of the Senate than a man who spent 36 years here as a United States senator," he said, "And I can't imagine a current candidate for president, more familiar with and comfortable with the details of how the previous administration worked tirelessly to fight corruption in Ukraine and the current administration has failed to than my predecessor."

Later on Tuesday he tweeted: "I’m a lawyer, and here’s what I know: Trials have witnesses, and the witnesses have to be relevant to the case. It isn’t complicated. The President is on trial here, not anyone with the last name Biden. VP Biden and Hunter Biden are not relevant witnesses."