Ambassador Lynne Tracy was able to visit Gershkovich this week for only the second time since he was detained in March on espionage charges, which he, his employer and Washington all deny.

Russian embassy staff were given access on the same day to Vladimir Dunaev, a Russian national in pre-trial detention in Ohio on cybercrime charges.

The Kremlin said this week there were "certain contacts" with the United States over Gershkovich's case but "they must be carried out and continued in complete silence".

(Reporting by Reuters)