The tomato suspension agreement, which sets the rules for such imports, establishes a so-called reference price, or minimum sale price. Historically, importers say that has included all costs associated with getting tomatoes from the border to distributor warehouses, like wages and inspection fees. But some are now asking the U.S. Department of Commerce to have those costs be added to the reference price.

“This might add up to 20% to 25% of the Nogales shipping cost of tomatoes,” said Lance Jungmeyer of the Nogales-based Fresh Produce Association of the Americas, which opposes the proposed new interpretation. “And that’s significant.”

Recently a number of U.S. representatives, including five from Arizona’s congressional delegation, sent a letter also opposing the proposal to Commerce. Florida tomato growers say the interpretation is necessary to protect domestic growers from what they describe as the threat of dumped Mexican tomatoes.