Former Trump campaign manager Paul Manafort arrives for arraignment on a third superseding indictment against him by Special Counsel Robert Mueller on charges of witness tampering, at U.S. District Court in Washington, U.S. June 15, 2018.

Both trials are related to the lucrative work Manafort did for a pro-Russia political party in Ukraine, years before he became chairman of Donald Trump 's presidential campaign in 2016. Manafort, who was jailed without bond in June after being accused of witness tampering, has pleaded not guilty in both cases.

Manafort, 69, a longtime Republican consultant, is scheduled to next go on trial Sept. 17 in Washington, where he is accused of money laundering and failing to register as an agent for a foreign government. Charges accusing him of trying to tamper with witnesses were lodged in June, months after the original case was filed.

Jurors in that case began deliberations Thursday morning. They have yet to reach a verdict on bank fraud and tax crime charges.

That number of exhibits dwarfs the fewer than 400 pieces of evidence Mueller's team of prosecutors introduced at Manafort's ongoing trial in U.S. District Court in Alexandria, Virginia.

Special counsel Robert Mueller has given lawyers for ex-Trump campaign chief Paul Manafort "well over 1000 proposed exhibits," or pieces of evidence, which prosecutors want to show jurors at Manafort's next federal criminal trial in Washington, D.C., a court filing revealed Thursday.

Judge Amy Berman Jackson, who will preside over the Washington trial, had given Manafort's lawyers and Mueller until next Monday to file a joint pretrial statement. That statement would detail their respective lists of proposed exhibits, list their expert witnesses, give an estimate of how long their respective cases will take to present to the jury, and propose jury instructions.

But in their filing Thursday, Manafort's lawyers asked Jackson to give them another week on that task.

Jackson later Thursday gave them just four extra days — until Aug. 24.

The judge also said in an order that she "encouraged" Mueller "to review the exhibit list closely with an eye towards streamlining the presentation of its case."

Manafort's attorneys had cited how long it will take to review the large volume of exhibits proposed by Mueller, most of which were not part of the Virginia trial.

"Review of these materials will be time-consuming," Manafort's defense team wrote.

"The task simply cannot be accomplished while Mr. Manafort's legal team is engaged in trial before Judge [T.S.] Ellis" in Virginia, they added. "It is unknown when the jury will return a verdict."

Defense lawyers also noted the trial in Virginia "has not allowed" them enough time to confer with Mueller's team about the joint pretrial statement that is due next week.

This is the second time Manafort's team has requested an extension of that deadline. Jackson previously had asked both sides to submit their statement on Aug. 1.

Mueller's office, which declined to comment, has previously expressed irritation with Manafort's team for asking for that extension.

In July, Mueller's team told Jackson that it had given the defense "a roadmap" of its case by divulging all the information deemed necessary for the joint pretrial statement.

"With each submission to the defense, the government asked the defense to alert it to its position, so the government could inform the Court" in time to meet the original deadline, Mueller's prosecutors wrote.

"Not once did Manafort respond, in any way, to any of the government's disclosures," prosecutors said.

Manafort's lawyers did not immediately respond to a request for comment from CNBC.

Jackson previously has said she would be opposed to postponing the start of the trial beyond Sept. 17.