U.S. Secretary of State Mike Pompeo demanded the release Wednesday of a retired U.S. Marine detained in Russia on espionage charges and wants to know why he was arrested.Speaking to reporters in Brazil where he is attending the inauguration of the country's new government, Pompeo also said the U.S. expects to get consular access to the detained American, who has been identified as 48-year-old Paul Whelan."We are hopeful within the next hours we will get consular access to see him and get a chance to learn more," Pompeo said. On Monday, Russian Federal Security Service (FSB) officials said Whelan had been detained on December 28 "while carrying out an act of espionage," and that they have opened a criminal probe.They provided no further details, but Russia's state-run TASS news agency said that Whelan faces up to 20 years in prison if convicted.Whelan is employed as director of global security at Borg Warner, an American automotive parts supplier. Whelan's family learned of his arrest only after it was reported by Russian state news outlets, prompting the family to contact congressional representatives and U.S. diplomats."We are deeply concerned for his safety and well-being," the family said. "His innocence is undoubted and we trust that his rights will be respected."Whelan's arrest coincides with several spy scandals that have exacerbated tensions between Russia and the West, including the poisoning of former double agent Sergei Skripal and his daughter in Britain. Russian citizen Maria Butina was convicted in the U.S. recently for acting as an illegal foreign agent. Butina pleaded guilty to acting under the direction of a Russian official to establish relationships with influential Americans. News of Whelan's detention came less than 24 hours after Russian President Vladimir Putin issued a New Year's greeting to U.S. President Donald Trump in which he said Moscow is amenable to a continuing dialogue with Washington on a range of topics.In 2016, Izvestia, a Kremlin-aligned news outlet, reported that there were 13 U.S. citizens in Russian jails at the time. The Kremlin has not since published any details on other Americans currently in Russian detention.