American retail, restaurant and agriculture groups weighed in on Thursday against a U.S. NAFTA modernization proposal that could pave the way for U.S. seasonal produce growers to file anti-dumping cases against Mexico, according to letters sent to Trump administration officials.

Talks to overhaul the North American Free Trade Agreement resume this weekend in Mexico, the second round after U.S. President Donald Trump’s renewed threats to withdraw from one of the world’s biggest trade blocs.

In one letter seen by Reuters, sent to U.S. Commerce Secretary Wilbur Ross and Trade Representative Robert Lighthizer on Thursday, retailers argued that the U.S. proposal to allow more complaints about the dumping of perishable produce would have “dangerous implications for U.S. businesses and consumers.”

Seasonal fruit and vegetable growers in the southeastern United States have come under increasing pressure from year-round Mexican imports under NAFTA and are seeking the ability to pursue anti-subsidy and anti-dumping cases or seek temporary import quotas.

Small growers have not been able to bring such cases because they do not represent a big enough share of U.S. production to qualify under current U.S. trade laws.

Lighthizer, in NAFTA negotiating objectives published by his office, said he would seek a “separate domestic industry provision for perishable and seasonal products” in trade cases.

The retailers and food industry groups argued that American producers could be left open to retaliatory measures if more complaints were to be filed, for instance, against avocados, tomatoes and other produce imported from Mexico.

The letter was signed by large trade groups including the National Council of Chain Restaurants, National Restaurant Association, National Retail Federation, Retail Industry Leaders Association and the Fresh Produce Association of the Americas.

A separate letter was sent on Wednesday by 26 U.S. agriculture groups – addressing Ross, Lighthizer, Agriculture Secretary Sonny Perdue and Gary Cohn, the top White House economic adviser. It too urged American negotiators to abandon the fresh produce proposal because it risks damaging U.S. producers.

“Once seasonal tariffs were put in place for tomatoes, for example, Mexico or Canada may initiate trade cases of their own on any of a wide range of U.S. agricultural products, beginning a tit-for-tat cycle that could broadly limit agricultural trade,” the letter said.

“At a time of low commodity prices in much of the United States, US agriculture can hardly afford to see a primary market disrupted,” it added.