A letter from Ukraine’s U.N. Ambassador Sergiy Kyslytsya to Secretary-General Antonio Guterres and members of the U.N. Security Council was obtained by The Associated Press ahead of a closed council meeting late Wednesday requested by Britain, France and the United States on Iran’s sale of hundreds of drones to Russia.

The three Western countries strongly back Ukraine’s contention that the drones were transferred to Russia and violate a 2015 U.N. Security Council resolution that endorsed the nuclear deal between Iran and six key nations — the U.S., Russia, China, Britain, France and Germany — aimed at curbing Tehran’s nuclear activities and preventing the country from developing a nuclear weapon.