On Wednesday, the Trump administration dramatically joined the UK Government in blaming Russia for the attack.
In response they announced another round of sanctions targeting Russia, which will take effect within two weeks.
As a result the Russia ruble collapsed to its lowest value since 2016.
Kremlin spokesman Dimitry Peskov criticised the sanctions as “categorically unacceptable”.
He added: “We deny in the strongest terms the accusations about the possible connection of the Russian state to what happened in Salisbury.
“This is out of the question.
“Russia did not and does not have, and could not have, any connection to the use of chemical weapons.”
The new US sanctions will stop Russian state-owned firms from buying certain American electoronic devices.
They are being imposed in response to a 1991 US law which requires export controls to be imposed on any country found to have used chemical weapons.
On March 4 Sergei Skripal, a former Russian spy who had worked for UK intelligence, and his daughter Yulia were found unconscious on a bench in Salisbury.
Both survived and were later released from hospital.
However Dawn Sturgess, a UK national, also came into contact with the novichok nerve agent in June and subsequently died.
The UK Government swiftly blamed the Russian state, with Theresa May saying: “It is highly likely that Russia was responsible.”
Former Foreign Secretary Boris Johnson added that it is “overwhelmingly likely” that the attack was directed by Russian President Vladimir Putin.
In response the UK expelled 23 Russian diplomats as part of what Mrs May described as action to “dismantle the Russian espionage network in the UK”.
Another 150 diplomats were expelled by UK allies in a show of solidarity.