Moscow has been trying with mixed success to improve battered U.S. -Russia ties since Donald Trump won the White House in 2016, and Russia's political elite was quick to chalk up a summit last month between Trump and Vladimir Putin as a victory.
Vladimir Vasilyev, a senior researcher at the Institute of the U.S. and Canada in Moscow, said the Americans were strengthening sanctions "from an element of pressure into an ultimatum".
Clark went on to call the Skripal case a convenient excuse, saying the USA has a history of finding reasons to sanction Moscow no matter what.
The U.S. State Department said Wednesday that Congress had been notified and that the new sanctions would go into effect on August 22.
The sanctions came as an eagerly-watched contest for a previously safe Republican seat in the United States congress went to the wire, leading to speculation that voters were turning against Donald Trump and could punish the Republican Party at mid-term elections. The Reuters news agency said they would restrict sensitive national security controlled goods to Russian Federation.
In a statement issued by its embassy in Washington, Russia called charges that Moscow employed chemical weapons "far fetched" - arguing the USA lacked evidence, and repeating demands for a new investigation into the poisoning.More news: God Of War’s Massive New Game Plus Mode Is Coming This Month
"We are tough on Russian Federation, and at the same time we are committed to maintaining relations because there are important things at stake here", a senior state department official said.
The sanctions enacted so far this year, and the threat of more, have already inflicted pain on Russia's middle class.
"Let us welcome the United Sanctions of America!" It kicked out 60 diplomats - the highest number of any country.
Although the United States says it is sanctioning Moscow over the Sergei Skripal case, the measures are actually due to internal U.S. politics which have led to a "sanctions war" in Washington, writer and journalist Neil Clark told RT.
Kremlin spokesman Dimitry Peskov criticised the sanctions as "categorically unacceptable".
In response, Peskov said it was too early to talk about counter measures, suggesting the Kremlin does not want to escalate the situation too soon.More news: Kris Aquino dazzles in yellow at 'Crazy Rich Asians' premiere in Hollywood
FILE - In this March 13, 2018, file photo, police officers guard a cordon around a police tent covering a supermarket vehicle park pay machine near the spot where former Russian spy Sergei Skripal and his daughter were found critically ill following exposure to the Russian-developed nerve agent Novichok in Salisbury, England.
In March former Russian spy Sergey Skripal and his daughter, Yulia Skripal, were poisoned with a Soviet-designed nerve agent known as Novichok.
Moscow has angrily rejected any involvement in the poisoning, plunging diplomatic relations with London into crisis.
Konstantin Kosachev, chairman of the foreign affairs committee, said the U.S. is behaving like a "police state, threatening and torturing a suspect to get evidence".
"We once again flatly reject any accusations regarding the possible involvement of the Russian state in what happened in Salisbury".
"Sanctions are the USA weapon of choice", Trenin wrote on Twitter.More news: Liverpool goalkeeper Loris Karius given standing ovation upon Anfield return
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