Republican senators and Democratic House impeachment managers doubled down Sunday on their positions on calling witnesses in the Senate impeachment trial of President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE, with Republicans dismissing it as a stalling tactic and Democrats insisting the Senate and the public are entitled to additional information.

Sen. Tom Cotton Tom Bryant CottonRenewed focus on Trump's Supreme Court list after Ginsburg's death Republicans call for DOJ to prosecute Netflix executives for releasing 'Cuties' Loeffler calls for hearing in wake of Netflix's 'Cuties' MORE (R-Ark.) said he was unsure of whether the Senate would vote to call witnesses but dismissed the idea on CBS’s “Face the Nation.”

"I’m not going to vote to approve witnesses because the House Democrats have had lots of witnesses. ... We listened to [House Intelligence Committee Chairman] Adam Schiff Adam Bennett SchiffTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies MORE [D-Calif.] drone on for three days, and the president's lawyers in just two hours demolished the case they had made," he said.

"They’re not upset that they haven’t had witnesses. They’re upset that their witnesses haven’t said what they want them to say," he added.

Sen. James Lankford James Paul LankfordMcConnell works to lock down GOP votes for coronavirus bill Charities scramble to plug revenue holes during pandemic Warren calls for Postal Service board members to fire DeJoy or resign MORE (R-Okla.), meanwhile, decried the call for witnesses as an attempt to prolong the trial as the chamber’s GOP majority seeks a speedy resolution.

“They wanted to move as fast as possible, and now they want to slow down the trial as much as possible in the Senate,” Lankford said on ABC’s “This Week.” “That’s just a very odd political strategy for them more than a fact-finding strategy.”

The vote on whether to call witnesses, which will likely take place this week, has become a central question in the impeachment trial. Democrats tried to include a requirement to vote on individual witnesses and documents in the organizing resolution that set the rules for the trial, but Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE (R-Ky.) had the votes to shoot down the amendments and punt the question of witnesses until after both sides deliver opening statements.

Democrats want to hear from former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE and acting White House chief of staff Mick Mulvaney Mick MulvaneyMick Mulvaney to start hedge fund Fauci says positive White House task force reports don't always match what he hears on the ground Bottom line MORE. Last week, they dismissed an idea floated by Republicans of "witness reciprocity," which would allow Republicans to call a witness they want to hear from, such as former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE's son Hunter Biden, in exchange for each Democratic witness called.

Sen. Amy Klobuchar Amy KlobucharThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - White House moves closer to Pelosi on virus relief bill EPA delivers win for ethanol industry angered by waivers to refiners It's time for newspapers to stop endorsing presidential candidates MORE (D-Minn.) quoted the musical “Hamilton” in explaining her request for witnesses, saying, “I want to hear from the men — to quote the Founding Fathers musical — to hear from the men in the room where it happened. ... That is people like Mr. Bolton and Mick Mulvaney.”

Democrats say Bolton and Mulvaney have firsthand knowledge of Trump's dealings with Ukraine but that Hunter Biden's testimony is irrelevant because he doesn't. Trump's allies contend that information from Hunter Biden could unravel the beginnings of the investigation.

The House’s impeachment managers also defended how the trial has been conducted thus far, with Rep. Zoe Lofgren Zoe Ellen LofgrenTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence DHS opens probe into allegations at Georgia ICE facility House passes legislation to boost election security research MORE (D-Calif.) calling on Trump to “get a grip” after a Sunday morning tweet in which he said Schiff “has not paid the price, yet, for what he has done to our Country.”

"The president has a tendency to say things that seem threatening to people," Lofgren said on CNN's "State of the Union."

Lofgren also called on senators to vote for witnesses as a “favor” to the country, saying, "I think the country wants a complete picture. The senators have an opportunity to do it. ... I think they would be doing themselves a favor as well as the country a favor."

Schiff also responded to Trump’s tweet, saying it was “intended as a threat.”

"It is going to be very difficult for some of these senators to stand up to this president. It really is. There's just no question about it," Schiff said on NBC’s “Meet the Press.” "I want to acknowledge that, and I don't want to acknowledge it in a way that is offensive to them, but I do want to speak candidly about it."

Schiff also called on Chief Justice John Roberts to rule on the relevance of testimony from Hunter Biden if he is called to testify.

“We have a very capable justice sitting right behind me who can make decisions about the materiality of witnesses,” he said. “We trust the Supreme Court chief justice to make those decisions.”