Retired U.S. Marine Paul Whelan, who was detained and accused of espionage, speaks inside a defendants' enclosure during a court hearing on June 20 to consider an appeal to extend his detention in Moscow. (Maxim Shemetov/Reuters)

Looking gaunt and vexed, American Paul Whelan appealed on Thursday to President Trump to intervene in his high-profile case, six months afterRussian authorities jailed the former Marine on spy charges.

Speaking from a glass enclosure during an appeal hearing, in which a Moscow court extended his stay in custody until the end of August, Whelan asked for help from Trump, who has remained quiet on the case despite his claim that he is a master hostage negotiator

“Mr. President, we cannot keep America great unless we aggressively protect and defend American citizens wherever they are in the world,” Whelan told reporters as guards tried to shush him. Still addressing Trump, he continued, “Please tweet your intent on this.” 

Whelan, who holds citizenship in Canada, Britain and Ireland in addition to the United States, asked the governments of his four countries for help, saying he is the victim of an “absurd political kidnapping.” 

Russian security agents arrested Whelan, 49, in late December, seizing him in his upmarket Moscow hotel room during what he says was a personal trip as a tourist. Despite claims by the Kremlin that he was caught “red-handed,” no evidence has been presented, exasperating U.S. officials.

If found guilty, Whelan could face up to 20 years in a Russian prison. 

Whelan’s court-appointed Russian lawyers say a flash drive containing “state secrets” was planted in his pants pocket by a Russian friend who is tied to the country’s security services. They declined to go into detail Thursday about which of Russia’s powerful security agencies he worked for. “This man did this to Paul so he could get promoted,” lawyer Olga Karlova said. 

On Thursday, Whelan repeated his claims that he was being maltreated and denied some of his rights to force a confession “for a crime that did not occur.” Whelan said he was being denied reading material, medical care and full consular access. He also said he was being physically harassed, but did not go into detail, saying he was prohibited from doing so. 

His lawyers said that Whelan has an English-speaking cellmate, and that he writes a letter a day to his family — letters that sporadically make their way to the United States and Canada. 

They also warned that Whelan’s fate is very much in limbo. By Russian law, he could stay behind bars — he is housed in a notorious pretrial detention center in Moscow — through the end of December, which would mark a full year since his arrest. But even this time frame could be challenged if the investigator continues to provide no evidence. 

By extending his custody, the judge ruled Thursday against granting Whelan house arrest with an electronic tag on his ankle. Lawyer Vladi­mir Zherebenkov had offered the American a place to stay in one of his two Moscow apartments. Failing that, Whelan could technically stay at his own cost in his hotel room at the Metropol near the Kremlin, where he was arrested. 

“They’re worried that if he moves to the hotel, representatives from his countries will try to take him away,” Zherebenkov said, referring to the judge’s decision. 

U.S. national security adviser John Bolton said he had a productive meeting with Whelan’s sister, Elizabeth, late last week, amplifying a growing chorus of voices in Washington who are concerned about Whelan’s situation. 

Softening for a brief moment on Thursday, Whelan hesitantly smiled, saying the officers in prison were treating him better than before. He also wished his dog, Flora, a happy birthday.