MEXICO CITY (AP) — U.S. officials said Monday they are still far from agreement with Mexico over that country’s plans to ban imports of genetically modified corn for human consumption.

Mexico has said it may eventually ban GM corn for animal feed as well, but expressed hope that some sort of joint agreement could be reached to study the issue.

The U.S. Trade Representative’s office said Mexico had proposed some changes, but “these changes are not sufficient.”

“Mexico’s proposed approach, which is not grounded in science, still threatens to disrupt billions of dollars in bilateral agricultural trade, cause serious economic harm to U.S. farmers and Mexican livestock producers,” the office said in a statement.

U.S. farmers are worried about the potential loss of the single biggest export market for U.S. corn. Mexico has been importing U.S. GM feed corn for years, buying about $3 billion worth annually.

Mexico cites health concerns, but such a trade restriction could violate the U.S.-Mexico-Canada free trade agreement.

Mexico hopes to stave off a full-fledged trade complaint under the agreement on the corn issue as well as a dispute over Mexico’s energy sector.

The United States says Mexico is unfairly favoring its state-owned electricity and oil companies over American competitors and clean-energy suppliers. Canada also has joined in that complaint.