Federal prosecutors on Thursday accused former President Donald J. Trump’s lawyers of trying to employ an arcane law governing the use of classified material to “intentionally derail” the timing of his trial on charges of mishandling national security documents and obstructing efforts to retrieve them.

The accusation of deliberate foot-dragging by the prosecutors in the office the special counsel, Jack Smith, was the latest salvo over the schedule of the classified documents trial, which — after weeks of contentious arguments — is set to begin in May in Federal District Court in Fort Pierce, Fla.

In court papers filed to Judge Aileen M. Cannon, who is presiding over the case, the prosecutors accused Mr. Trump’s legal team of seeking to delay by at least three months a crucial step in how the government intends to prepare the classified documents at the heart of the proceeding for review by the defense.

That request for a delay, wrote one of the prosecutors, Jay I. Bratt, “threatens to upend the entire schedule established by the court” and “amounts to a motion to continue the May 20, 2024, trial date.”

The timing of any trial is a milestone that is often hashed out in tense negotiations. But the classified documents trial is particularly contentious given that it has to compete on the calendar with Mr. Trump’s three other criminal trials — in Washington, Georgia and New York — that are set to go in front of juries starting in March.

Further complicating matters, all the proceedings are unfolding as Mr. Trump, who is now the front-runner for the Republican presidential nomination, campaigns again for the country’s highest office.

Almost from the moment that Mr. Trump and two of his aides were charged, Mr. Smith’s team has been trying to move the documents case along expeditiously. Their concern is that if Mr. Trump is re-elected, he might be in a position to pardon himself or have his attorney general simply dismiss the charges.

Mr. Trump’s lawyers, by contrast, have repeatedly sought to slow the proceedings. They initially asked Judge Cannon to start the classified documents trial after the 2024 election. They made an even more extraordinary request in Mr. Trump’s other federal case — in which he stands accused of plotting to overturn the 2020 election — asking for a trial date in April 2026.

In a separate motion filed on Thursday, Mr. Trump’s lawyers also asked to delay the election interference case, saying they wanted to postpone their deadline for filing pretrial motions to Dec. 8 from Oct. 9. “This case presents numerous novel and complex legal issues,” wrote John F. Lauro, one of Mr. Trump’s lawyers. “Counsel has been diligently researching these questions and preparing appropriate pretrial motions, but requires a brief extension of time to complete this process.”

The government’s filing in the classified documents case, beyond asking Judge Cannon to resolve the scheduling issues, also gave a glimpse of the scope and nature of the evidence at the center of the proceeding.

So far, prosecutors said, they have turned over about 1.28 million pages of unclassified materials to the defense, including about 200 transcripts of witness interviews and grand jury appearances. They have also made several transcripts available to Mr. Trump and his team in which witnesses discuss classified issues.

Judge Cannon ruled this month that any discussions Mr. Trump has with his lawyers about classified discovery evidence must take place in an SCIF, or sensitive compartmented information facility, in Miami.

But in their filing, prosecutors said there were at least nine documents that were so sensitive they were not allowed to be stored in the SCIF in Florida and would be made available to Mr. Trump’s lawyers only in Washington. The latest spat over scheduling emerged from the intricacies of a law known as the Classified Information Procedures Act, which sets out rules for how government secrets can be safely presented at a public trial. Legal experts have long predicted that the thorny nature of CIPA, as the law is often called, would result in time-consuming legal fights like the one that has erupted.

The dispute began last week, when Mr. Trump’s lawyers accused the government of failing to hand over all the materials it was obliged to under the discovery process. The lawyers said they needed that material to gear up for a related fight over whether prosecutors should be able to redact some of the classified documents at the heart of the case before providing them to the defense.

Mr. Trump’s lawyers, claiming that the government was effectively rushing a complex process, asked Judge Cannon to push back any attempt to even broach the subject of redactions until January. His lawyers in the election interference case have made a similar request, asking to postpone the consideration of redactions on the limited amount of classified material in that proceeding, too.

Prosecutors have not yet responded to the second proposal. But in their response on Thursday to lawyers in the documents case, they said the delay was both excessive and unnecessary.