Russia has allowed U.S. pork imports from two firms of Chinese-owned producer Smithfield Foods Inc after it received additional guarantees, Russia's veterinary watchdog (VPSS) said on its website.

Russia banned most meat imports from the United States early last year because of concerns over the use of the feed additive ractopamine.

Its decision to allow imports only from Smithfield Foods Inc, which was bought by China's Shuanghui International Holdings last year, comes amid the worst East-West crisis since the Cold War over Russia's decision to annex Crimea from Ukraine.

Russia agreed to allow imports of U.S. pork from two Smithfield firms in early March, but asked for more food safety guarantees about the refrigerators used for supplies.

The VPSS website says that out of 179 firms which produce and store pork in the U.S., Russia is now ready to accept it from two Smithfield firms and from four owners of refrigerators.

Other firms are still not allowed to ship the product to Russia, according to the website.

VPSS was not available for additional comment.

U.S. President Barack Obama said Washington was considering sanctions against key economic sectors in Russia, including financial services, oil and gas, metals and mining and the defence industry, if Russia made military moves into eastern and southern Ukraine.

(Reporting by Polina Devitt, editing by Jason Bush and William Hardy)