The leaders of the United States, France, Germany and Britain say they are united in blaming Russia for a nerve agent attack on former spy Sergei Skripal.

U.S. President Donald Trump said it looks like Russians were behind the poisoning of the former spy.

The U.S. sanctioned 19 Russian individuals and five groups for meddling in the 2016 presidential election, the U.S. Department of the Treasury said in a statement on Thursday. The treasury said that Russia's recent use of a military-grade nerve agent in the U.K. demonstrates the "reckless and irresponsible conduct" of the Russian government.

Entities sanctioned include Russia's federal security service and the Russian internet research agency, the statement said, as well as other Russian intelligence services. Also targeted is Russian Businessman Yevgeniy Viktorivich Prigozhin.

Russia's Deputy Foreign minister said that Moscow views the new U.S. sanctions calmly, and is preparing retalitory measures.

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A senior Trump official said that Russian behavior on the World stage is troubling, and the U.S. campaign to force change is not over.

In the rare joint statement condemning Russia, world leaders President Donald Trump, President Emmanual Macron, Chancellor Angela Merkel and Prime Minister Theresa May say "there is no plausible alternative explanation" to Russian responsibility in the March 4 attack in England.

"We, the leaders of France, Germany, the United States and the United Kingdom, abhor the attack that took place against Sergei and Yulia Skripal in Salisbury, U.K., on 4 March 2018," the statement said.

"This use of a military-grade nerve agent, of a type developed by Russia, constitutes the first offensive use of a nerve agent in Europe since the Second World War.

They say Russia's failure to respond to Britain's "legitimate request" for an explanation "further underlines its responsibility."

"It is an assault on U.K. sovereignty and any such use by a State party is a clear violation of the Chemical Weapons Convention and a breach of international law. It threatens the security of us all."

Russia's Deputy Foreign Minister Sergei Ryabkov said on Thursday that neither Russia nor the Soviet Union had run a program to develop the 'Novichok' nerve gas which Britain says was used to poison a former double agent, the Interfax news agency reported.

Britain has expelled 23 Russian diplomats and suspended high-level contacts with Moscow over the incident.

Russia is expected to take retaliatory measures soon. Russia has denied any involvement and Foreign Minister Sergei Lavrov accused London of behaving in a “boorish” way, adding that this was partly due to the problems Britain faces over its planned exit from the European Union next year.

Lavrov said Russia’s response would come “very soon” but be conveyed to British officials first, an apparent contradiction of an earlier report by state news agency RIA that said Lavrov had promised to expel British diplomats.