On Wednesday, the US State Department announced a new round of sanctions targeting Russian exports of dual-purpose electronics and other national security-controlled equipment, which will come into effect on August 22.
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The ruble is stabilising as the market realises that the new USA sanctions proposed by the White House are not as painful as the penalties proposed earlier by US senators, analysts at Alfa Bank said in a note.
The administration has imposed fresh sanctions on Russia in retaliation for the poisoning of former Russian double agent Sergei Skripal and his daughter in Salisbury in March.
In March, the Trump administration ordered 60 Russian diplomats - all of whom it said were spies - to leave the United States and closed down Russia's consulate in Seattle in response to the Skripal case. The poison was smeared onto the front door of Skripal's home in Salisbury, England, and United Kingdom authorities have blamed the assassination attempt on the Kremlin.
Speaking after the State Department announcement, Royce said the administration was "rightly acting to uphold global bans on the use of chemical weapons".
The use of chemical or biological weapons, which is a violation of worldwide law, triggers sanctions under US law.
Russian authorities played down the importance of new USA sanctions, saying they have tools to maintain financial stability, after a new round of US penalties sent the rouble plunging to a two-year low.
Zakharova told reporters at a briefing that no evidence had been presented to prove Russia's blame, and that the pretext for the new round of sanctions had been made up.
Speaking during a trip to Russia's far east, Mr Medvedev said: "I would not like to comment on talks about future sanctions, but I can say one thing: If some ban on banks' operations or on their use of one or another currency follows, it would be possible to clearly call it a declaration of economic war".
The Associated Press, citing an unnamed State Department official, says that sanctions "include the presumed denial of export licenses for Russian Federation to purchase many items with national security implications".
British Prime Minister Theresa May welcomed the decision.
The Trump administration has also already responded to the nerve agent poisonings.
The Finance Ministry said on Thursday there was no threat to financial stability, a statement markets interpreted as a signal Moscow had no immediate plans to channel any of its $458 billion worth of reserves into propping up the rouble. With these sanctions, the exports will be presumptively denied.
After tests, scientists at the UK's military research lab, Porton Down, found the couple had also been exposed to Novichok.
Some former officials told The Post, however, that the order seemed more like a "a cover-your-behind exercise" for the administration than meant to seriously deter foreign powers.
Last week, a group of Democrat and Republican senators introduced a bill that would impose some of the toughest sanctions ever placed on modern Russian Federation.
The announcement of sanctions caused Russian stock markets to drop dramatically on opening and the ruble reached its lowest point since November 2016.
It remains unclear if lawmakers will succeed in passing the bill, with Congressional leaders having seemed unconvinced.
Trump caught flak from Democrats and Republicans alike for what many saw as his unsettling embrace of Putin last month at their Helsinki summit, when Trump appeared to disavow his own intelligence agencies' assessment on Moscow's election interference.