The White House today threw it weight behind the United Kingdom in the case of a nerve agent attack on a former spy and his daughter, saying it shares the British assessment that Russia is responsible for the attack.

It also said that the UK's decision to expel 23 Russian diplomats in retaliation for the alleged attack was a 'just response'.

"The US stands in solidarity with its closest ally, the UK. The US shares the UK's assessment that Russia is responsible for the reckless nerve agent attack on a British citizen and his daughter, and we support the UK's decision to expel Russian diplomats as a just response," White House Press Secretary Sarah Sanders said.

British Prime Minister Theresa May yesterday expelled 23 Russian diplomats -- in the 'single biggest expulsion' in more than 30 years -- and suspended high-level bilateral contacts, saying Moscow was 'culpable' of the nerve agent attack.

Former Russian spy Sergei Skripal, 66, and his daughter Yulia, 33, were found collapsed after being poisoned last week.

Both remain in a serious condition along with a police officer who came in contact with the same substance.

Russia denies its involvement in the attempted murder. Sanders said the attack fits into a pattern of behaviour in which Russia 'disregards the international rules-based order, undermines the sovereignty and security of countries worldwide, and attempts to subvert and discredit Western democratic institutions and processes'.

"The US is working together with our allies and partners to ensure that this kind of abhorrent attack does not happen again," she said.  -- PTI

IMAGE: A police officer stands at a cordon around the bench where former Russian intelligence agent Sergei Skripal and his daughter Yulia were found after they were poisoned, in Salisbury, on Wednesday. Photograph: Henry Nicholls/Reuters