CHICAGO, July 27 (Reuters) - U.S. poultry producers say they face prolonged economic pain from avian flu despite going months without infections in flocks, as China and some smaller importers fail to lift trade bans implemented during the nation's worst-ever outbreak of the virus.

The lingering bans, imposed last year to prevent the spread of the disease, constrain the $6 billion U.S. export market for poultry meat as producers also grapple with limited labor, lower chicken prices and uncertain costs for feed.

The Chinese market is particularly important for U.S. companies because it is the primary destination for items like chicken feet that Americans generally do not eat, industry officials said.

Pilgrim's Pride CEO Fabio Sandri warned on Thursday that Beijing may extend its ban even as other countries resume trade. Mostly owned by JBS SA, the company is one of the world's largest chicken producers.

"Other than China, we expect to see further easing of export restrictions during Q3," Sandri said on an earnings call.

China, South Africa and the Dominican Republic each maintain bans on poultry from 37 states that previously reported infections, U.S. Department of Agriculture (USDA) records show.

Mexico, the top overall market for American poultry meat, has largely lifted trade bans, though shipments from Colorado, Washington state and counties in a few other states are blocked, records show.

China's failure to lift bans 90 days after states eliminate avian flu from farms violates the Phase 1 trade agreement signed with former President Donald Trump in 2020, industry officials said.

The U.S. Trade Representative's (USTR) office declined to comment and China's General Administration of Customs did not respond to a request for comment.

The USDA had no updated comment. It said last year it was committed to ensuring restrictions are in line with international agreements and lifted as quickly as possible.

Wayne-Sanderson Farms, the third-largest U.S. poultry producer, told Reuters many of its facilities are in states that should have been reapproved for exports months ago.

"China continues to be less than forthcoming when it comes to state reapprovals," the company said. "We have opportunity losses that are in the millions of dollars between white meat, dark meat and paws."

U.S. exports of chicken feet, or paws, to China are down 27% by volume through May, after rising in 2022, USDA data show.

Chicken producers Perdue Farms and Tyson Foods have also highlighted trade restrictions. Tyson reports quarterly earnings Aug. 7.

"Several key countries have not yet returned to normal patterns of business with the United States," Perdue said in a statement to Reuters. "We are eager for our industry's long-standing business relationships to resume."

Avian flu has disrupted trade globally as the virus spread. Japan this summer suspended poultry purchases from two states in Brazil, the world's largest chicken exporter, after cases in backyard animals.

Under guidelines from the World Organization for Animal Health, regional or national trade bans are applicable if the highly lethal virus infects a commercial farm.

United Nations agencies have said global outbreaks in poultry raise concerns the virus might adapt to infect humans more easily.

NEARLY $1 BLN EXPORT HIT

The U.S. outbreak began last year and has wiped out nearly 59 million chickens, turkeys and other birds. The last infection in a commercial flock was in April, though, and some states facing export restrictions have not detected commercial cases since 2022, USDA data show.

Export losses from the outbreak total $895 million, the USA Poultry and Egg Export Council said on Tuesday. That is down from $1.3 billion for the previous record outbreak in 2015, after the U.S. convinced trading partners to narrow trade restrictions.

The council, an industry group, said USDA sent China reports requesting it end restrictions on 14 states, including major producers North Carolina and Arkansas.

"They haven't budged on it," said Greg Tyler, council president.

In a March report, the USTR said the government submitted reports to China for states deemed to be free of avian flu. The Phase 1 trade pact requires China to resume imports within five days of receiving the information, the report said.

U.S. industry officials suspect China's delay is political amid heightened tensions with Washington.

States saddled with trade bans, including Texas and Maryland, said they sought information from USDA.

"We're certainly concerned about not being able to export our products when we know we've got a good clean product," Texas Agriculture Commissioner Sid Miller said in an interview.

(Reporting by Tom Polansek in Chicago. Additional reporting by Dominique Patton in Beijing; Editing by Caroline Stauffer and Marguerita Choy)