WASHINGTON- Russia's payment of already-overdue international debts in dollars involved fresh funds, not any money immobilized in the U.S. system, a senior U.S. official said on Friday, noting the United States had not authorized any such transactions.

"The main concern was are they going to use funds that were immobilized in the U.S. or use the money they have been using to prop up the rouble and the war effort.

It appears it came from that pile of money because we didn't authorize any transactions involving the immobilized funds in the U.S.," the official said.

(Reporting by Andrea Shalal Editing by Chizu Nomiyama)