- Video report by ITV News Correspondent Emma Murphy
Britain has backed a US decision to impose sanctions on Russia after determining that Moscow used a nerve agent in an attempt to kill former spy Sergei Skripal and his daughter.
Foreign Secretary Jeremy Hunt praised the US, saying the measure showed there "is a price to pay" for using chemical and biological weapons.
The State Department said the sanctions - which have been condemned by the Kremlin - will be imposed on Russia because it used a chemical weapon in violation of international law.
These sanctions could reinforce President Donald Trump's claim that despite investigations into Russian election meddling and accusations of collusion, his administration has in fact clamped down on Moscow.
In response to the US move, Vladimir Putin's spokesman Dmitry Peskov said the decision runs contrary to the "constructive" atmosphere at the Trump-Putin summit last month.
"In our view, these and earlier restrictions are absolutely unlawful and don't conform to international law," Mr Peskov said.
Russia Foreign Ministry spokeswoman Maria Zakharova said on Thursday that the restrictions are a new attempt to "demonise Russia," adding that "ultimatums against Russia are useless."
Skripal and his daughter were poisoned by Novichok, a military-grade nerve agent, in Salisbury in March.
Britain has accused Russia of being behind the attack, which the Kremlin vehemently denies.
Downing Street welcomed the move by the US, with a Number 10 spokesman saying: "The UK welcomes this further action by our US allies.
"The strong international response to the use of a chemical weapon on the streets of Salisbury sends an unequivocal message to Russia that its provocative, reckless behaviour will not go unchallenged."
And in a tweet on Thursday, Mr Hunt said: "If we are going to stop chemical and biological weapons - including nerve agents - becoming a new and horrific 21st cent norm states like Russia that use or condone their use need to know there is a price to pay.
"Thank you USA for standing firm with us on this."
Announcing the move, US State Department spokeswoman Heather Nauert said: "The United States, on August 6, 2018, determined under the Chemical and Biological Weapons Control and Warfare Elimination Act of 1991 (CBW Act) that the Government of the Russian Federation has used chemical or biological weapons in violation of international law, or has used lethal chemical or biological weapons against its own nationals."
- What are the sanctions?
The Trump administration's sanctions on Russia are set to come in two waves.
The first round of new measures will be implemented on or around August 22 following a 15-day Congressional notification period.
They will involve a ban on licenses to export key high tech items such as electronics, avionics and other sensitive national security goods to Russia.
Russia will then have a 90-day period to respond and unless it provides “reliable assurances” that chemical weapons will not be used again, and also agrees to UN inspections, the second round could have even further implications.
These sanctions could then include downgrading diplomatic relations, suspending flights to the US by state airline Aeroflot and cutting off many more exports and imports.
- Hasn't the US already imposed sanctions?
The US has already expelled dozens of Russian diplomats after agreeing with the UK’s assessment that Moscow was “highly likely” to have been responsible for the nerve agent attack.
Moscow then responded in turn by ordering its own expulsion of foreign diplomats on Russian soil.
The Kremlin strongly refutes it was involved in the attack, with Russian President Vladimir Putin stating it was "unthinkable that we would do such a thing" back in March.
- How has Russia responded to the new sanctions?
The Kremlin condemned the sanctions for "far-fetched accusations" as "draconian" as the Russian embassy in the US hit back on Thursday morning.
The department said it had become "accustomed to not hearing any facts or evidence" and said: "We continue to strongly stand for an open and transparent investigation of the crime committed in Salisbury."
It is unlikely, however, that Moscow would allow no-holds-barred UN inspections of this nature, according to ITV News Washington Correspondent Robert Moore.
- What else has happened since the Salisbury attack?
Since the March attack where Sergei Skripal and his daughter Yulia were found slumped on a park bench after coming into contact with nerve agent Novichok, two other British nationals, who had no ties to Russia, have been poisoned by the substance.
Dawn Sturgess, 44, and partner Charlie Rowley, 45, both came into contact with the agentwhich left them hospitalised at the end of June in Amesbury, Wiltshire.
Ms Sturgess died eight days after being poisoned, but Mr Rowley survived the ordeal.
Mr Rowley said the nerve agent took just 15 minutes to poison Ms Sturgess after she sprayed the “oily” substance onto her wrists, believing it was perfume he had given her as a gift.