The US has said Russia used a chemical weapon to try to assassinate ex-spy Sergei Skripal in Britain, and it is to impose new sanctions.
The State Department said the sanctions will be imposed on Russia because it used a chemical weapon in violation of international law.
Former Russian spy Sergei 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.
Since the March attack, two other British nationals with no ties to Russia have been poisoned by the substance.
Following a 15-day congressional notification period, the sanctions will take effect on or around August 22, according to a statement from the State Department.
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 attack.
According to US media reports, the new measures include a ban on granting licenses to export sensitive national security goods to Russia.
A second round – kicking in three months later unless Russia provides “reliable assurances” it will not use chemical weapons again and agrees to UN inspections – could include downgrading diplomatic relations, suspending flights to the US by state airline Aeroflot and cutting off many exports and imports.
Responding to new sanctions on Russia, a Downing Street spokesman said: “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.”
The Government has been consistent in pointing the finger of blame at Moscow for the poisoning using novichok – a military-grade nerve agent developed by the former Soviet Union.
Two more people – Dawn Sturgess and Charlie Rowley – were subsequently treated for exposure to novichok after Ms Sturgess reportedly picked up a discarded perfume bottle thought to have contained the agent.
Rowley, like the Skripals, recovered from the attack but Ms Sturgess, his partner, died.
The Guardian this week reported the Government is set to submit an extradition request to Moscow for two Russians suspected of carrying out the Salisbury nerve agent attack.
It said the Crown Prosecution Service (CPS), which has been preparing papers, has completed the process and was ready to file.
In a statement setting out the new US action, the State Department said: “Following the use of a Novichok nerve agent in an attempt to assassinate UK citizen Sergei Skripal and his daughter Yulia Skripal, 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.
“Following a 15-day Congressional notification period, these sanctions will take effect upon publication of a notice in the Federal Register, expected on or around August 22, 2018.”