The agreement, co-signed by Russia, the United States, and Britain, assured Ukraine that its "territorial integrity or political independence" would be respected in return for its decision to move all its nuclear weapons to Russia.

The independent republic of Ukraine inherited the world's third-largest nuclear arsenal when the Soviet Union formally dissolved in 1991.

"On President (Volodymyr) Zelensky's initiative I officially requested UNSC member states to immediately hold consultations under Article 6 of the Budapest memorandum," Foreign Minister Dmytro Kuleba tweeted.

The Security Council must address "practical steps to guarantee the security of Ukraine," he wrote.

Article 6 of the 1994 agreement says Moscow, Washington, and London "will consult in the event a situation arises" that puts Ukraine's security under threat.