Washington (CNN) Senate Minority Leader Chuck Schumer on Sunday said the key to a fair impeachment trial is getting four Republican senators to join Democrats in shaping the proceeding.

"I hope, pray, and believe there's a decent chance that four Republicans will join us. If they do, we will have a fair trial," Schumer said on ABC's "This Week."

As Congress continues to discuss impeachment this week, senators have been preparing for a trial where they will decide whether President Donald Trump should be removed from office. At least 20 Republicans would have to break with Trump to provide the 67 votes needed to remove him from office, but if enough peel off they could provide Democrats with the 51 votes needed for key wins, such as to compel witnesses, demand documents and push through other procedural motions Democrats may seek during a trial.

Two articles of impeachment passed last month against Trump remain in limbo after congressional leaders hit what Senate Majority Leader Mitch McConnell called an "impasse" on the rules of a trial.

On Sunday, Schumer said the trial will be a "sham" -- and predicted there will be blowback for Trump and other Republicans -- if Democratic-proposed rules and witnesses aren't approved.

"If the President is acquitted through a sham trial, through a mock trial, where there are no witnesses, where everything is covered up, that will not stand him well with the American people and it will not stand the Republicans with the American people," the New York Democrat said.

Responding to McConnell's proposal to first have evidence presented in the trial before hearing from potential witnesses, Schumer said that was something that would only happen in a fantasy story.

"Where but in Alice and Wonderland do we hear all the arguments and then maybe have the evidence, the witnesses, and the trial?" Schumer asked.

The two articles of impeachment passed in December against Trump charged him with abuse of power for withholding nearly $400 million in US military aid and a White House meeting from Ukraine while pressuring the country's president to investigate a potential political rival, and obstruction of Congress for thwarting the House's investigative efforts.