The American visit comes as the Russian military claimed to have recaptured Sudzha - a key town in the Kursk region that Ukraine invaded last year in a surprise attack.

Russian forces have begun an assault on the town of Sudzha, the main population center in the Kursk region that was captured by Ukraine last year, a top Russian commander said on Tuesday. The advance puts Moscow on the verge of ending the first invasion of Russian territory since World War II.