The Trump Administration said it would impose new sanctions against Russia as punishment for its use of a nerve agent in an attempt last March to assassinate British citizen and ex-Russian spy Sergei Skripal and his daughter.

A terse release from the State Department said that the United States had determined Russian responsibility for the attack in Salisbury, England — a British conclusion the Administration had already accepted — under a 1991 US law on biological and chemical weapons use that requires the president to impose sanctions.

Russia has denied responsibility for the attack.

A State Department official said the sanctions could have a significant impact on trade with Russia.

They are structured to fall in two halves. The first part includes a prohibition of licenses on sending some goods to Russia, such as electronic devices. It will have limited impact since it replicates restrictions already on the books.

But if Russia does not agree to stop using chemical and biological weapons within 90 days and agree to let UN monitors conduct inspections, a second, more punishing round of sanctions kicks in.

It would cut off almost all trade between the two countries and could include the suspension of Aeroflot flights into the United States.