MOSCOW (Reuters) - A former U.S. Marine held in Russia on suspicion of spying called on U.S. President Donald Trump and the leaders of Britain, Canada and Ireland to help him as he appeared in court at an appeal hearing on Thursday.

Paul Whelan, who holds U.S., British, Canadian and Irish passports, was detained in a Moscow hotel room on Dec. 28 and accused of espionage, a charge he denies. If found guilty, he faces up to 20 years in jail.

Whelan said last month that he had been threatened by a Russian investigator in custody and harassed, accusations that added to strains in U.S.-Russian relations.

“Mr president (Trump), we cannot keep America great unless we aggressively protect and defend American citizens wherever they are in the world,” Whelan told reporters at a hearing in Moscow on Thursday.

“I am asking the leaders and governments in Ottawa, Dublin, London and Washington for their help and public statements of support,” he said, standing inside a glass cage.

Whelan’s lawyer has said his client was framed and that he was given a flash drive by an acquaintance that he thought contained holiday photos, but that actually held classified information.

Whelan was in court on Thursday to appeal against the extension of his custody until Aug. 29. The court ruled against him.