U.S. Ambassador to Russia Jon Huntsman on Wednesday visited the retired U.S. Marine who has been detained on espionage charges in Russia.
He also spoke on the phone with the family of Paul Whelan, 48, according to a State Department statement that did not release any details of the call "due to privacy considerations for Mr. Whelan and his family.''
It did say, "Ambassador Huntsman expressed his support for Mr. Whelan and offered the embassy's assistance.''
Access was granted just hours after U.S. Secretary Mike Pompeo said he expected an explanation of why the American was arrested and demanded his release if the detention was not appropriate.
On Monday, Russian Federal Security Service (FSB) officials said Whelan had been detained Dec. 28 "while carrying out an act of espionage" and that a criminal probe had been ordered.
The FSB provided no further details, but Russia's state-run TASS news agency said Whelan faces up to 20 years in prison if convicted.
Whelan is employed as director of global security at BorgWarner, 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 coincided 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.
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 was amenable to a continuing dialogue with Washington on a range of topics.
In 2016, Izvestia, a Kremlin-aligned news outlet, reported 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.
VOA's Peter Cobus in Moscow contributed to this report.