The federal judge overseeing former President Donald J. Trump’s classified documents case formally scrapped her own May 20 start date for the trial on Tuesday but declined to set a new one, saying there was much more work to be done before a jury could hear the charges.

The decision by Judge Aileen M. Cannon to delay the start of the trial was more or less a foregone conclusion given the number of legal issues that remain unresolved less than two weeks from the date she had originally set.

In a brief order, Judge Cannon wrote that picking a new date at this point would be “imprudent and inconsistent with the court’s duty to fully and fairly consider” what she described as “the myriad and interconnected” pretrial issues that she had not yet gotten to.

Those included several of Mr. Trump’s pending motions to dismiss the case and a host of thorny questions surrounding how to decide what sorts of sensitive information can be revealed at the trial under a law known as the Classified Information Procedures Act.

Mr. Trump is charged in the case with mishandling and illegally holding onto classified material after leaving the White House and with obstructing the government’s repeated efforts to retrieve it from him. Prosecutors have indicated that some of the material he was found to have kept included information about military plans and American nuclear capabilities.

Judge Cannon first signaled that she was inclined to make some “reasonable adjustments” to the timing of the trial as far back as November. Then in March, she held a hearing in Federal District Court in Fort Pierce, Fla., specifically to discuss the trial calendar.

Even though Mr. Trump’s lawyers told her on the eve of that hearing that they could be ready to go to trial in August if necessary, Judge Cannon made no further decisions about scheduling matters until her order issued on Tuesday.

The decision about when to start a trial is an important one for any judge to make, but the timing of Mr. Trump’s classified documents trial — and of his other federal case, in which he stands accused of plotting to overturn the 2020 election — has more than the usual significance.

That is because if the federal proceedings are pushed until after the election in November and Mr. Trump were to win the race, he could order the Justice Department under his control to drop the charges.

As part of her order on Tuesday, Judge Cannon, who was placed on the bench by Mr. Trump in his waning days in office, laid out a series of hearings and filing deadlines that reached into late July. The calendar she set made it all but impossible that the case could go in front of a jury even by August, the time frame to which Mr. Trump’s lawyers had already agreed.

Throughout the case, Judge Cannon has given Mr. Trump’s legal team wide berth in defending him, often granting an audience to legal motions that many federal judges would have rejected out of hand or decided on the merits of written filings alone.

One of the most surprising hearings she included in her newly issued calendar was a two-day proceeding in late June to decide who should be considered as part of the prosecution team. In January, Mr. Trump’s lawyers filed court papers suggesting that a vast swath of the U.S. national security establishment — including top intelligence and defense officials — were part of the team.

The point of that move by Mr. Trump’s team was to seek additional discovery information about any contacts that those officials may have had with prosecutors in the office of the special counsel, Jack Smith. Mr. Trump’s lawyers were seeking to bolster their defense strategy that members of the so-called “deep state” had colluded in bringing the classified documents case against Mr. Trump.

Judge Cannon also scheduled a separate but potentially explosive hearing in late May to consider arguments about whether Mr. Smith had launched what is known as a “selective and vindictive prosecution” against Mr. Trump’s co-defendant, Walt Nauta. The hearing is likely to include Mr. Trump’s own claims of selective prosecution because Mr. Nauta, one of his personal aides, included them in his own filing.

Echoing one of Mr. Trump’s political talking points, his lawyers have been claiming for months that the special counsel unfairly brought an indictment against him even though other public figures, like President Biden, have been found in possession of classified materials but avoided being charged. Another significant aspect of Judge Cannon’s new schedule was her decision to postpone until mid-June the deadline for Mr. Trump’s lawyers to submit a critical filing containing a detailed inventory of the classified materials that they intend to introduce at the trial.

That inventory is consequential because it will set in motion what will eventually be a pitched battle between the defense and prosecution over what sorts of classified materials the jury will hear about — a fight that will involve balancing issues of public access and national security, and that could take months to complete.

The initial filing deadline for that inventory was supposed to have been Thursday, but late on Monday night, Judge Cannon set aside that date without picking a new one.

Her decision came directly after Mr. Trump’s lawyers asked again for the deadline to be pushed back, saying they needed more time and raising allegations that Mr. Smith’s team had failed to preserve the integrity of the boxes of documents that sit at the heart of the case.