The use of ractopamine, which is used to stimulate livestock growth and make meat leaner, has been banned in 160 countries, including Russia, RIA Novosti reported.
The U.S. government and meat industry lobbyists say the additive is safe in certain quantities.
A spokesman for the U.S. Meat Export Federation said in the first 11 months of 2012 the United States had exported approximately $280 million worth of pork and $305 million worth of beef to Russia. The ban could mean large financial loses for the United States, RIA Novosti reported.
Andrea Mead, a spokeswoman for U.S. Trade Representative Ron Kirk, said the U.S. government was "deeply concerned" by the decision.
"These actions threaten to undermine our bilateral trade relationship," she said.
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