TORONTO -- A U.S.-Canadian citizen who’s been detained in Russia for nearly a year will have to wait even longer for his day in court.

Paul Whalen, a former U.S. marine who was born in Ottawa, was arrested on espionage charges while attending a wedding a Moscow on Dec. 28, 2018, but has yet to stand trial in the matter. A judge told him Tuesday he would need to wait until March 29 before his trial could begin.

“They're allowed to hold him for up to 18 months without having a trial and they appear to be wanting to do that,” David Whelan, Paul’s brother, told CTV News from Newmarket, Ont.

If convicted, Whelan could spend up to 20 years in prison.

“There still has been no evidence provided by the (Federal Security Service of the Russian Federation) to the court about Paul’s charges,” David said.

Russian federal agents said Whalen had a flash drive with classified information on it, but Whalen said he thought it contained holiday photos given to him by a friend.

On Monday, diplomats from the U.S., Canada, the U.K. and Ireland -- all countries where Whalen holds citizenship -- met with Whalen and said he remains in good mental health, but accuses the guards of mistreatment.

"Paul has been unable to make a telephone call to his parents,” said Bart Gorman, the deputy chief for the U.S. mission to Russia, told reporters.

“For 12 months he has made multiple requests, but they have gone unanswered. At this time of the year, when the concept of family is paramount, we call on the Russian government to allow Paul to make a phone call to his mother and father for Christmas and the New Year."

Global Affairs Canada on Tuesday called for Russia to stop using Whelan’s detainment as a political tool.