Senate Minority Leader Chuck Schumer (D-NY) detailed which documents he’d like to see the administration produce for the upcoming Senate impeachment trial in a Monday letter to his fellow senators, and pointed specifically to the recent release of redacted Ukraine-related emails from the Office of Management and Budget.

The letter comes amid a standoff between Senate Majority Leader Mitch McConnell (R-KY) and Democrats over whether the Senate should come to an agreement about seeking additional evidence before moving to a trial.

McConnell, who has been pushing for a short trial, says that such an agreement should wait until after the Senate has moved through the initial stages of the proceedings, as was done in the 1999 Clinton impeachment.

Schumer, in his letter Monday, argued that the circumstances in that proceeding were different than those facing the Senate now.

“In 1999, the Senate could not reach an initial agreement on witnesses because a number of Senators on both sides of the aisle, including then-Majority Leader Lott, believed that the facts in the Clinton case had been fully established before the trial. The House Managers’ proposed witnesses had already testified multiple times under oath, and transcripts of their testimony were available to the Senate,” Schumer said.

In this case, Schumer argued, “the President has ordered that witnesses with direct knowledge, and documents containing directly relevant evidence, be withheld.”

He argued that delaying a decision on witnesses and documents would have a “practical effect” of “foreclos[ing] the possibility of obtaining such evidence because it will be too late.”

The trial is expected to start in January, though it’s unclear if the current stalemate will delay it beyond that. Speaker Nancy Pelosi (D-CA) has said she’d wait until she had a clearer picture of what the trial would look like before transmitting the impeachment articles to the Senate. She’s downplayed the idea of using such a delay as leverage to force a fairer trial, however.

Schumer’s letter detailed examples of specific documents he’d want the administration to produce from the White House, the State Department and the OMB.

They include White House emails relating to Trump’s phone calls with Ukraine President Volodymyr Zelensky, any documents linked to the concerns raised by National Security Council officials about Trump’s Ukraine conduct, and the communications documenting a reported effort to create an after-the-fact justification for the hold on military aid to Ukraine.

From the State Department, Schumer wants emails and documents that have been described by witnesses in the House impeachment inquiry and that are being withheld by the administration.

On Friday evening the OMB released heavily redacted emails that showed its efforts to implement Trump’s freeze on the aid after his July 25 call with Zelensky where Trump brought up his demands for investigations. The emails were released under court order due to a Freedom Information Act lawsuit brought by a non-profit.

“The December 21st release of partially-redacted versions of these communications in response to the FOIA lawsuit further underscores why the Senate must review all of these records in unredacted form,” Schumer said Monday.

Read his letter below: