The second round of sanctions could cut far deeper, including blocking all American bank loans to Russian entities, an outright ban on USA exports to Russia, and suspension of diplomatic relations. The Russian embassy in Washington has accused the United States of running a "sanctions assembly line".
Former Foreign Secretary Boris Johnson added that it is "overwhelmingly likely" that the attack was directed by Russian President Vladimir Putin. He went on to describe it as a "kind of game where everyone has to show how tough they are on Russian Federation".
Clark went on to call the Skripal case a convenient excuse, saying the United States has a history of finding reasons to sanction Moscow no matter what.
The Trump administration said on Wednesday that it would soon impose new sanctions against Russia in response to the attempted assassination in March of a former Russian spy living in England and his daughter.
Sanctions will go into effect on August 22 after a mandatory waiting period, the State Department said.
While Kremlin spokesman Peskov suggested the Kremlin was still weighing how to respond to the sanctions, other Russian officials were less circumspect.
The first, which targets US exports of sensitive national-security related goods, comes with deep exemptions and numerous items it covers have already been banned by previous restrictions.
"In practice this will mean we are imposing a "presumption of denial" upon export licences for USA -origin national security-sensitive goods and technology to any Russian state-owned or state-funded enterprise", the official said in a conference call with reporters.
"There is local panic on the currency market", BCS Brokerage said in a note. It kicked out 60 diplomats - the highest number of any country.
The White House has not said whether the poisonings came up during his meeting with Putin.
"We consider the tying of new restrictions - which as previously we consider illegal - with the affair in Salisbury to be categorically unacceptable", Peskov told reporters during his daily telephone briefing.
Donald Trump's administration explicitly blamed Russian Federation for carrying out the chemical attack on Sergei and Yulia in Salisbury, Wilts, in what was believed to be an assassination attempt.
In June, two more people were taken to hospital after being exposed to the nerve agent.
Skripal, a former colonel in Russia's military intelligence service, and his 33-year-old daughter were found slumped unconscious on a bench in the southern English city of Salisbury in March after a liquid form of the Novichok type of nerve agent was applied to his home's front door.
"We believe linking new [U.S.] restrictive measures, which we continue to consider illegitimate, to the Salisbury case is totally unacceptable", Peskov said, according to the Russian news agency TASS, referring to the suspected poisoning of a former spy and his daughter in the United Kingdom.
Moscow has angrily rejected any involvement in the poisoning, plunging diplomatic relations with London into crisis.