U.S. officials have prodded China repeatedly for a faster and more open system for deciding whether to approve the import of new GMO crop varieties. China approved only one strain last year, a soybean strain from Bayer’s Crop Science division, compared with three varieties approved in 2015.

“The trend is moving in the wrong direction in terms of the product being approved in the past few years,” says Gao Yong, a Monsanto official who is cochair of the agriculture group of the American Chamber of Commerce in China. Gao doesn’t know why the approval rate is slipping.

The courts are still cleaning up the mess from Chinese rejection in 2013 of cargoes of U.S. corn on the grounds the U.S. included an unapproved GMO variety (MIR162) from Syngenta. U.S. regulators approved the strain in 2010.

The two nations agreed during the Trump-Xi meeting in Florida last month to a 100-day effort to improve trade relations. White House press secretary Sean Spicer says, “Beef exports and additional market access in China” were among “a lot of topics that got put on the table” for discussion. China agreed last September to accept U.S. beef, banned since 2003, but technical issues remain.

The American Chamber of Commerce says it typically takes six years to win Chinese clearance of a GMO variety, twice as long as other major nations. Government decisions on approval of biotech applications are made once a year. The panel of experts who review applications used to meet three times a year, but now they are required to meet at least twice a year.

U.S. ag exports to China increased by 125% in the past decade, as Beijing became the largest U.S. customer for farm products, says USDA Chief Economist Robert Johansson.

This article was produced in collaboration with the Food & Environment Reporting Network, an independent, nonprofit news organization producing investigative reporting on food, agriculture, and environmental health.