STANFORD, California - The Bush administration wisely backed away this month from formally challenging Europe's ban on genetically modified foods. It made no sense to antagonize Europeans over the food they eat when they are pivotal to more weighty matters, such as a new resolution on Iraq.

Still, Washington's threat that it would file a case against the European Union at the World Trade Organization had palpable benefits. Even the countries with the most hostile policies on engineered food - France and Germany among them - took steps toward allowing the European Union to work on replacing the blanket ban with a new system for tracing and labeling engineered food.

But the decision to back off also means that American farmers are still denied access to the lucrative European market. European consumers still pay more for food than they should. And developing countries that could most benefit from engineered crops are still frightened that losing their "engineering-free" status will make it impossible to export food to Europe.

Yet the science on food safety is as certain as it ever gets: There is no known danger from eating engineered food.

Having backed down, the Bush administration will find it hard to make the threat of going to the trade organization credible again and to continue the momentum toward removing Europe's ban. But even harder for the administration will be keeping domestic politics at bay.

The biggest threat to the success of the U.S. strategy on engineered foods is in the American heartland, which is angling for a fight with Europe over the ban as the 2004 elections approach. Senator Charles Grassley of Iowa called the decision to defer a trade dispute "the usual snobbery" of a State Department "more concerned about international sensitivities than the American farmer." Two tactics should guide the effort to open Europe's markets. One is to let the Europeans lead their own reform.

The engineered foods available to consumers today mainly benefit farmers who can grow them at lower cost. These foods look and taste the same as their traditional counterparts. For rich consumers in Europe willing to pay a bit more, it is easy to focus on hypothetical risks and shun these products. But the next generation of engineered foods, already nearing the marketplace, will have healthful benefits for consumers - fruits that contain cancer-fighting lycopene, for instance - and this will make it harder for European countries to bar all these foods.

During the furor last summer over Zambia's rejection of genetically modified corn, prominent European politicians were forced to declare that these foods were safe - a blatant contradiction of Europe's own policies.

The other tactic is outreach to the developing world. In the poorest nations, agriculture provides the livelihood of most of the population, and agricultural research proves that genetic engineering can make crops that poor farmers grow both healthier and more productive.

Yet research on engineered crops and support for farmers who grow them lack money, not only in U.S. agricultural development and extension programs but also at the international agricultural research centers that were the engine of the first green revolution. In the last decade American support for international agricultural research has declined considerably.

An American program that would finance agricultural research on novel uses for genetically modified crops in developing countries would help those countries and could eventually help open European markets.

An American-led effort to pry open those markets would backfire. But one led by a developing country could succeed, as Europe considers the moral issues posed by barring food from a country which needs to sell its crops to survive. So far, few developing countries (South Africa is one exception) allow commercial planting of engineered crops. The United States needs to overcome the fears of the developing nations by growing such crops there and demonstrating how they could transform agriculture.