WASHINGTON — The May 16 deadline set by the Food & Drug Administration to comment on sweeping food-safety changes to farms and processing facilities is impossible to meet, the United Fresh Produce Association and more than 80 other groups told FDA Commissioner Margaret Hamburg in an April 11 letter asking for a deadline extension.

But the fresh produce industry is not asking for a new date. Instead, the groups are asking FDA to hold off on setting a deadline until three interrelated regulations — the foreign supplier verification, preventive controls for animal feed and third-party auditing proposals — are published so the industry can have a better idea of how FDA’s new food-safety program will affect domestic and foreign businesses.

Since FDA proposed, on Jan. 16, the produce-safety and preventive controls regulations, the produce industry has been scrambling to collect data FDA requested, while analyzing the far-reaching implications of a new FDA Food Safety Modernization Act program.

“Based on our current analysis, it would be impossible for any interested party to meaningfully comment on these two proposed rules by the current deadline of May 16, 2013, given they propose such a substantial overhaul of the structure of food-safety regulation; the sheer size of the regulations lengthens the time necessary for analysis,” said the groups in the four-page letter.

The two rules and supporting documents total more than 1,000 pages, and produce industry experts are now analyzing hundreds of scientific, economic and industry references to see how the rules interrelate and what challenges they may provide for association members, the letter said.

“There were lots and lots of extra questions in the preamble,” on a range of issues such as the appropriateness of the microbial standard for water,” said Ray Gilmer, vice president of issues management and communications at United Fresh.

“As FDA has admitted, they need data,” Mr. Gilmer explained. “They’re being asked to write regulations where’s there’s not a lot of data,” he said. The industry knows the answers to these complex questions are likely to shape a final rule.

On top of that, the industry is awaiting the release of the proposed foreign supplier verification rule, which will require importers to verify foods they are importing meet the same level of public health protection as for domestic growers and processors. The other two rules on animal feed and accredited third-party certification will also affect the fresh and fresh-cut produce industry.

The April 11 letter relays another message to the FDA commissioner: Don’t significantly alter the rules without allowing stakeholders another chance to comment on the changes.

“It would not serve the integrity of the rulemaking process nor, indeed, the important policy objectives embodied in FSMA, to significantly modify the January 16 proposed rules without affording stakeholders the opportunity to review and comment on those modifications,” the letter said.

Some of the stakeholders calling for more comment time include: American Mushroom Institute, California Citrus Mutual, California Grape & Tree Fruit League, Canadian Produce Marketing Association, Florida Fruit & Vegetable Association, National Potato Council, Northwest Horticultural Council, Sunkist Growers Inc., Texas International Produce Association, U.S. Apple Association and Western Growers.