The leaders of France, Germany, Britain and the United States issued a joint statement on Thursday condemning a chemical attack on a Russian former double agent in England and blaming Moscow for it.
Moscow has denied any responsibility for the attack on Sergei Skripal and his daughter Yulia. Britain has expelled 23 Russian diplomats, and Moscow is expected to retaliate.
"We, the leaders of France, Germany, the United States and the United Kingdom, abhor the attack that took place against Sergei and Yulia Skripal in Salisbury, U.K., on 4 March 2018," the statement said.
"This use of a military-grade nerve agent, of a type developed by Russia, constitutes the first offensive use of a nerve agent in Europe since the Second World War.
"It is an assault on UK sovereignty and any such use by a State party is a clear violation of the Chemical Weapons Convention and a breach of international law. It threatens the security of us all."
The four nations called on Russia to provide full and complete disclosure of its Novichok nerve agent program to the Organisation for the Prohibition of Chemical Weapons.