(Adds National Chicken Council statement in paragraph 9)

By Missy Ryan

WASHINGTON, July 15 (Reuters) - China's decision to block some U.S. pork and poultry imports is a blow to exporters who rely on the Asian market for sales of products shunned by consumers at home, U.S. meat interests said on Sunday.

News this weekend that China's quarantine bureau had suspended pork and poultry from some U.S. plants -- following the discovery of salmonella-contaminated chicken and other products with growth agents or other additives -- struck another sour note in the two countries' trade ties.

Even as Americans grow more worried about the safety of the goods they buy from China, the Asian nation is seeking to extinguish fears about products from pet food to toothpaste, and to improve its image among the world's consumers.

Companies affected by the latest flap include some of the giants of American agriculture, including a unit of the private Cargill Inc., and Tyson Foods <TSN.N>, the leading U.S. producer of fresh beef and No. 2 producer of chicken and pork.

Thad Lively, a trade analyst at the U.S. Meat Export Federation in Denver, said China is a crucial market for animal products not typically consumed in the United States like "variety meats," which usually includes things like chicken feet and pig ears.

"Losing access to this market would be very damaging to the overall profitability of the U.S. pork industry," Lively said.

He chalked the recent problems up to "excessively restrictive" import rules that are not based on science.

"The perverse impact of this plant delisting policy is that China will have to continue to live with high domestic prices at the same time that they run the risk of opening a new trade dispute" with Washington, Lively said.

Richard Lobb, a spokesman for the National Chicken Council, said U.S. poultry exports were backed by U.S. law and Agriculture Department inspections. "We hope this action is limited and will be quickly resolved," he said.

Cargill spokesman Mark Klein said one growth additive in question, ractopamine, was common in the U.S. pork industry and had been approved by the U.S. Food and Drug Administration. That's not the case in China.

"While it has not been approved for use in China, we understand that steps are underway to get those approvals," he said in an e-mail message.

China had already blocked imports from several U.S. pork plants and put two others on probation, according to the U.S. industry.

Trouble for U.S. pork exporters reflects the frustrations of the meat industry, which has been battling to expand beef exports crippled since mad cow disease was discovered in the United States in 2003.

The Bush administration is also pushing China on that count. President George W. Bush pressed China to accept U.S. beef shipments during a visit by Vice Premier Wu Yi in May.

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