CHICAGO/BEIJING (Reuters) - Hundreds of U.S. meat plants granted access to China in a 2020 "Phase 1" trade deal with President Donald Trump are set to lose export eligibility on Sunday, threatening roughly $5 billion in trade to the world's largest meat market amid a renewed trade war.

Losing access to China would deal a fresh blow to American farmers after Beijing earlier this month imposed retaliatory tariffs on some $21 billion worth of American agricultural goods, including 10% duties on U.S. pork, beef and dairy imports.

Beijing requires food exporters to register with customs to sell in China. Registrations for almost 1,000 beef, pork and poultry plants, including some owned by Tyson Foods and Cargill Inc, are set to expire on Sunday, according to U.S. Department of Agriculture (USDA) records and Chinese customs data. That's roughly two-thirds of all those registered.

The companies declined to comment or did not respond to Reuters questions.

China has not responded to repeated requests from U.S. agencies to renew plant registrations, the USDA said in a report last week, potentially violating an obligation under the Phase 1 deal.

Registrations for some 84 plants lapsed in February and while shipments from affected plants continue to clear customs, the industry doesn't know for how long China will allow imports.

"The risk involved in shipping product with a looming expiration date is high," Joe Schuele, spokesperson for the U.S. Meat Export Federation told Reuters.

"The situation is certainly dire if [registrations for] these plants are not renewed. The situation has the attention of every exporter."

The USDA has made the expirations a priority issue in discussions with Beijing, Schuele added.

Shanghai port has also imposed stricter inspections and documentation for U.S. meat cargoes, the Federation told members in a bulletin seen by Reuters, with some containers subject to full unpacking and inspection, raising processing time and additional fees.

To be sure, there are no signs to suggest that Beijing is imposing a blanket ban. Several hundred plants have had their registrations renewed until 2028 or 2029, according to a senior diplomat based in Beijing.

The U.S. was China's third largest meat supplier last year after Brazil and Argentina, accounting for 590,000 tons or 9% of total imports.

The USDA and the Office of the U.S. Trade Representative did not respond to questions from Reuters on Thursday. China's Commerce Ministry and customs department did not respond to faxed questions.

China's foreign ministry redirected questions to other agencies without naming any.

The "Phase 1" trade deal, signed in 2020, ended the first U.S.-China trade war with a pledge from Beijing to boost its purchases of U.S. goods and services, including meat, by $200 billion over two years. China didn't reach the target, which was agreed shortly before the pandemic hit.

That year, 1,124 beef, poultry and pork processing plants or logistic facilities were registered with Chinese customs for export, according to USDA, gaining access to the world's largest meat importer. There are 1,842 facilities certified today, but slightly less than half will remain if Sunday's batch of registrations lapse.

China is obligated under the Phase 1 deal to revise its approved plant list within 20 days of receiving updated lists from USDA's Food Safety and Inspection Service, according to the Meat Institute, an industry group for U.S. meat processors. It is unclear whether the current delays constitute a violation of the deal.

The potential impact from lapsed licenses could total up to $4.13 billion for the beef industry and $1.3 billion for pork, the U.S. Meat Export Federation said in a daily bulletin.

Loss of access to China would be an especially hard blow for exporters of parts like chicken feet and pork offal, which are consumed less domestically.