MOSCOW -- Russian prosecutors have asked a Moscow court to find former Marine Paul Whelan guilty of espionage -- a charge Whelan and U.S. officials vehemently deny -- and sentence him to 18 years in prison.

Whelan's lawyer, Vladimir Zherebenkov, said on May 25 that the Moscow City Court set June 15 as the date to hand down its verdict after a high-profile trial that has strained ties with Washington.

"Frankly speaking, we are all in shock," Zherebenkov said outside the Moscow City Court, where the trial was held.

According to Zherebenkov, his client reacted "with dignity" to the prosecutor's demand, adding that, in all, 15 witnesses had testified at the trial.

"The prosecutor questioned its four witnesses, who were mainly operatives of the secret service, while defense questioned its 11 witnesses, who are people Whelan was in touch with while in Russia. All of them testified that Paul had not 'recruited' anyone and had never collect any secret information," Zherebenkov said.

The 50-year-old Whelan, who also holds British, Canadian, and Irish citizenships, again told the court in his final statement that he was not guilty.

Whelan was arrested in Moscow in December 2018 and in March this year went on trial, despite the coronavirus pandemic and diplomatic protests.

Prosecutors claim that a flash disc found in his possession contained classified information.

USB Drive

Whelan says he was framed when he took a USB drive from an acquaintance thinking it contained holiday photos and that the allegations of spying against him are politically motivated. He has also accused his prison guards of mistreatment.

The trial was held behind closed doors because the evidence includes classified materials, as well as because of measures taken to slow the spread of the coronavirus.

Whelan was head of global security at a U.S. auto-parts supplier at the time of his arrest. He and his relatives insist he visited Russia to attend a wedding.

U.S. officials have urged Moscow to release Whelan and criticized the Russian authorities for their "shameful treatment" of him.

After the sentencing demand, the U.S. ambassador in Moscow, John Sullivan, said "this secret trial is a mockery of justice."

"There is no legitimacy to a procedure that is hidden behind closed doors. It is not transparent, it is not fair, and it is not impartial," Sullivan said in comments tweeted by embassy spokeswoman Rebecca Ross.

With reporting by TASS, AFP, and Interfax