A Moscow court on Friday extended the detention for the American arrested at the end of December for alleged spying.

Paul Whelan, a former U.S. Marine, was detained in a Moscow hotel at the end of December. His arrest raised speculation that he could be swapped for one of the Russians being held in the United States. Whelan’s lawyer said his client had been handed a flash-drive with classified information that he had been unaware of.

The court in Moscow ruled to keep Whelan, who arrived in court under escorted by a masked man, behind bars for another three months pending the investigation.

Whelan has not been formally charged yet but spying charges in Russia carry up to 20 years in prison.

Meanwhile, the U.S. Embassy complained that Russian authorities are not letting Whelan sign and hand over a waiver that would allow consular officials to release more details about his case.

The embassy said it is the first time that the Russian Investigative Committee is not allowing a U.S. national in a Russian jail to pass on a signed privacy waiver form.

“Why is this case any different? Consular access without being able to do true consular support is not real access,” U.S. Embassy spokeswoman Andrea Kalan said on Twitter.