Across from a Capitol Hill impeachment hearing that President Trump and his allies loudly rebuked, members of the White House legal team and its top legislative aide huddled Wednesday with Senate Republicans over lunch to plot out a potential trial in the upper chamber.

White House counsel Pat Cipollone and Legislative Affairs Director Eric Ueland were among those who met with the Republicans for more than an hour behind closed doors off the Senate chamber.

Ueland said the conversation was part of an ongoing effort to keep in close contact with Senate Republicans as the impeachment process picks up speed in the House. Cipollone declined to comment on the meeting.

"We believe that the president's rights need to be expansively respected, including the opportunity to call witnesses and have the opportunity to cross-examine witnesses as part of a trial process," Ueland said. "The president wants his case made fully in the Senate, including the full trial and that's a point we are going to make consistently."

Senate Republicans emerging from Wednesday's lunch said it remains to be seen whether any witnesses are called in a Senate impeachment trial, along with other mechanics behind the process such as how long it could last.

"I think that [White House officials] just wanted to help us ... get an understanding of where they're coming from and how they see it," said Senate Majority Whip John Thune, R-S.D. "It's a fluid process ... there's a lot of uncertainty surrounding this."

The argument of whether to call witnesses goes to a central debate among Senate Republicans on how long a trial could take and what it could look like. Some Republicans, including Sen. Lindsey Graham, a key Trump ally, have warned that calling witnesses could force an impeachment trial to drag on.

Already, Trump has said he would like to force Rep. Adam Schiff (the chairman of the House Intelligence Committee) and the anonymous whistleblower at the center of the House impeachment inquiry to testify in the Senate.

"They'll make a request for witnesses, but that would have to be granted by the Senate," Graham said following a White House meeting last month on impeachment. And "I don't know what appetite there is in the Senate by either party to make this a long, drawn-out thing."

At that Nov. 21 meeting, Graham and a small group of Senate Republicans met with Cipollone and other top White House officials and discussed the potential for a two-week trial. However, that could be difficult if witnesses are called.

"This process doesn't need to take super long," Ueland said in light of the demands for witnesses. With shortcomings in the House process, "the way to address those, it's pretty easy ... and not a matter of months or years in order to elicit information, put witnesses on, lay out our case and move on ahead in the Senate."

Trump has rebuked the House impeachment inquiry, refusing to participate in a formal defense before investigating committees. On Dec. 1, Cipollone sent a letter to House Judiciary Committee Chairman Jerry Nadler rejecting an offer to participate in Wednesday's hearing examining findings in the probe.

An anonymous whistleblower called the alarm on a July 25 call between Trump and the Ukrainian president that is at the heart of the Democratic-led impeachment inquiry, raising concerns that nearly $400 million in military aid was withheld for a political favor. It triggered the formal inquiry and a widespread investigation by the House Intelligence Committee that entailed testimony from more than a dozen witnesses and a series of public hearings.

Trump has labeled the call "perfect."

Ueland, for his part, repeatedly called the House impeachment process "fatally flawed," and he hopes to address that concern in a potential trial.

The president "feels like he has had no opportunity to tell his side of the story or defend against the allegations, and at some point he should have the right to do that," Ueland said.

Senate Republicans leaving Wednesday's luncheon suggested the month of January is now being set aside for a potential impeachment trial.

"Best to plan for that," said Sen. Kevin Cramer, R-N.D.

Senate Republicans also agreed that it's likely Cipollone will represent the president in a trial, and the White House would use its current legal team to mount a defense.

Cipollone "seemed to have confidence that they had hundreds of years of legal defense [experience] in their White House team," said Sen. Roy Blunt, R-Mo.