LONDON -- The Wall Street Journal reporter detained in Russia is expected to appear in court in Moscow on Thursday for the latest hearing about extending his pre-trial detention.

Evan Gershkovich, a correspondent with the paper's Moscow bureau, was arrested in March and stands accused of "acting on the instructions of the American side" and collecting state secrets about the military.

The FSB filed a request to extend the journalist's detention for "an unspecified period of time" as he awaits trial, Emma Moody, the Journal's editor for Standards and Ethics, said in an email to staff on Wednesday, citing Russian media reports.

Russia's state media agency, TASS, reported a hearing on that request would be held Thursday, Moody said.

Gerskovich appeared in court in April and June for hearings to appeal his pre-trial detention, which had been approved through Aug. 30. Under Russian law, prosecutors are required to request his pre-trial detention be continued every few months.

The Biden administration and the Kremlin have both confirmed they are in discussions to find a possible deal to free Gerskovich, likely in a prisoner swap. But the U.S. has said so far there is little progress.

President Joe Biden, who spoke with Gershkovich's family in April, has said the detention was "totally illegal."

State department officials said the U.S. determined the journalist had been "wrongfully detained." The House of Representatives in June unanimously passed a resolution calling for the immediate release of Gershkovich and Paul Whelan, another American being held in Russia.

ABC News' Patrick Reevell and Shannon Crawford contributed to this story.