"The United States believes that Russia is responsible for two people in the United Kingdom using a military-grade nerve agent", Haley said of the ex-Russian spy and his daughter who are extremely ill.
Speaking at the UN Security Council on Wednesday, Haley said the U.S. agreed with the British government's assessment that Russian agents had used deadly chemicals in an attempt to kill 66-year-old Sergei Skripal and his daughter Yulia in Salisbury last week.
Haley added USA officials stood "in absolutely solidarity" with Britain after the country expelled 23 Russian diplomats on Wednesday, a move it announced in response to nerve agent attack.
Britain has said the toxin, which also poisoned a British police officer who attended the scene, was Novichok, a lethal nerve agent first developed by the Soviet military.
"The use of nerve agents under any circumstances is unacceptable and its use by a state would constitute a serious violation of worldwide law", said a spokesman for the United Nations chief.
Moscow has also warned that it will take retaliatory measures, and on Tuesday threatened to expel British media if the licence of its state broadcaster RT was threatened in Britain.
Sealed off Police and military vehicles at poisoned policeman Nick Bailey’s home PIC PA
Still, Russia has denied any culpability for the act, calling accusations of Kremlin involvement "nonsense". "It threatens the security of us all", the United States and European leaders said.
In retaliation, Prime Minister Theresa May ordered the expulsion of 23 Russian diplomats, a halt to meetings with top Russian officials and the cancellation of an upcoming visit by Russian Foreign Minister Sergei Lavrov. "They are now being worked on and will be adopted in the near future", Zakharova said.
"We call on Russian Federation to address all questions related to the attack in Salisbury", the four world powers said in their statement.
The attack on the former Russian spy, a British citizen, has revived fears of a new era of Cold War with Russia, with United Kingdom defence secretary Gavin Williamson admitting that relations with Russia were not good.
"If we don´t take immediate, concrete measures to address this now, Salisbury will not be the last place we see chemical weapons use".
"We would take no pleasure in having to constantly criticize Russian Federation". "It was an unlawful use of force".
Britain, which has received statements of support from the United States, the European Union and North Atlantic Treaty Organisation, has said it will seek to coordinate an global response to the attack.
Arsenal midfielder Jack Wilshere: 'I must repay Gareth Southgate's faith in me'
We are experimenting with some players we think we need to know who might come into the fringes of the squad'. He has no concerns that Harry Kane will miss the tournament because of a knee injury sustained last Sunday.