MOSCOW — Russia’s prime minister sternly warned the United States against stepped-up sanctions, saying Friday that Moscow would retaliate with economic, political, and unspecified ‘‘other’’ means.

The tough message from Prime Minister Dmitry Medvedev reflected growing dismay over announced US sanctions that have sent the Russian ruble plummeting to its lowest level in two years.

The State Department said Wednesday that Washington would impose new sanctions this month after determining that Moscow used nerve agent in March to poison a former Russian spy in England. Russia has denied involvement in the poisonings of Sergei Skripal and his adult daughter.

The State Department said the sanctions will include denial of export licenses for Russia to purchase many items with national security implications. Congress is considering limits on bank transactions.