The UK briefed the NATO ambassadors Wednesday on the use of a nerve agent in Salisbury on 4 March.
The UK confirmed the use of a military-grade nerve agent of a type developed by Russia and briefed Allies that it was highly likely that Russia was responsible، said a NATO statement.
"Allies expressed deep concern at the first offensive use of a nerve agent on Alliance territory since NATO's foundation.
Allies expressed solidarity with the UK، offered their support in the conduct of the ongoing investigation، and called on Russia to address the UK's questions including providing full and complete disclosure of the Novichok programme to the Organisation for the Prohibition of Chemical Weapons.
Allies agreed that the attack was a clear breach of international norms and agreements،" it said. "NATO has repeatedly condemned the use of chemical weapons in Syria and called on those responsible to be held to account. NATO regards any use of chemical weapons as a threat to international peace and security،" it added.