U.S. envoy to Moscow says Russia ties sunk to 'Mariana Trench' depths

FILE PHOTO: U.S. ambassador to Russia John Sullivan speaks with journalists after his meeting with Paul Whelan, a U.S. national arrested and accused of espionage, outside a detention centre in Moscow, Russia January 30, 2020. REUTERS/Evgenia Novozhenina/File Photo

(Corrects paragraph 25 to fix typographical error)

WASHINGTON (Reuters) - Russia's invasion of Ukraine has made John Sullivan's tough job as U.S. envoy to Moscow even harder as he grapples with the Kremlin's nuclear saber-rattling and threats to sever relations while keeping his embassy running on one-tenth the normal staff.