US District Judge Aileen Cannon, a Trump appointee, issued a preliminary order on Saturday and scheduled a hearing on the matter for Thursday, September 1 in West Palm Beach, Florida.
She said the preliminary order was warranted by “the exceptional circumstances presented”.
“The court hereby provides notice of its preliminary intent to appoint a special master in this case,” Judge Cannon said. The two-page order “should not be construed as a final determination,” she added.
The preliminary ruling comes less than 24 hours after a federal magistrate judge in the same court unsealed a redacted version of the FBI affidavit used to secure the search warrant for Mr Trump’s Mar-a-Lago estate.
Federal agents investigating missing White House records left with 20 boxes of documents, including 11 sets of classified material.
Judge Cannon ordered the government to file a public response to Mr Trump’s request by August 30.
She also directed the Department of Justice (DOJ) to file under seal a more detailed list of property seized from Mr Trump’s home and explain the status of the government’s own review of the material.
The sealed document must describe “any filter review conducted by the privilege review team and any dissemination of materials beyond the privilege review team,” she said.
Mr Trump’s lawyer and the DOJ were both directed to include in their filings “their respective and particularised positions on the duties and responsibilities of a prospective special master,” according to the order.
The DOJ did not immediately reply to a request for comment. Alina Habba, one of Trump’s lawyers, also did not immediately respond to a request for comment.
Mr Trump’s lawsuit, filed against the US government on August 22, is seeking to halt the FBI review of the documents until a neutral third party could review them.
He has denied wrongdoing and offered a variety of explanations for the presence of classified documents at his home. For example, he said he had a “standing order” to declassify records he took and that FBI agents may have planted evidence during the search.