America's farm lobbyists have long been pressing their government to launch a formal trade dispute against the European Union's ban on genetically modified crops. This week they got their way, as the US and more than a dozen allies started proceedings within the World Trade Organisation.

For US farmers - the world's top planters of GM crops - the case is a welcome chance to crack open a lucrative market. But the case may ultimately do their country more harm than good.

Now is a particularly bad time to embark on a dispute that will inflame anti-Americanism in Europe. In the broader, already deteriorating relationship with continental Europe, the US has much more important issues at stake, notably reviving the Doha round on trade and mending diplomatic relationships strained by the Iraq war. Moreover, a close look at the options reveals that each of the plausible outcomes from a dispute would leave the US worse off than before.

First, the US could pay the political costs of launching an inflammatory dispute and then lose. Most press accounts compare this case with one of the first disputes ever handled by the WTO: the EU's ban on beef that had been produced using hormones. The EU lost because its ban had no basis in science and in "comparable" areas of food policy it had adopted much less strict rules - a telltale sign that the ban was a protectionist gambit.

On the surface, the cases appear similar. Although the science on the health risks of GM food is contested, essentially all the credible evidence shows that these foods are safe, which would seem to indict the EU ban. But in critical ways the cases differ. Across the board, the EU is tightening food safety regulations in ways that seem irrational by standard cost/benefit tests but, crucially, are broadly non-discriminatory and consistent - the key tests for whether a trade ban is legitimate. Moreover, the GM ban is a temporary measure - unlike the permanent ban on beef hormones - and trade rules allow more flexibility for countries that implement temporary measures when they can claim the science is uncertain.

Second, the EU could change its rules in the middle of the dispute. For several years, EU bureaucrats have been designing a new set of standards that would "reopen" Europe's markets to GM foods if traders complied with onerous tracing and labelling requirements. This shift would make it harder for the US to win because trade laws are tolerant of labels that allow consumers to make the final choice. While the US might respond by dropping the suit, it would be more likely to redirect the dispute against the tracing and labelling rules. In the past, hotly contested trade disputes have usually taken on a myopic life of their own. Each side digs in and the political damage spreads.

Third is the most likely (and worst) outcome: the US could win. The victory would be Pyrrhic because the issues are fundamentally ones of morality and technology - they must be settled in the courts of consumer opinion. On this score, the beef hormones case is instructive. Even today, hormone-treated beef is no more able to find European consumers than it was before the US won its case; and the years of legal wrangling have led to counter-sanctions that have harmed a wide variety of unrelated products and industries. The antagonism over GM foods appears to be unfolding in much the same way.

A better strategy would have been to stay the course that US policy has followed ever since the controversy over GM crops broke out in the late 1990s. Time is on America's side because the technology is already proving itself in the marketplace and European opponents will find themselves increasingly isolated.

But now that Washington has pulled the trigger, what can be done? The greatest danger is that both sides of the Atlantic slide into a tit-for-tat retaliation. But a trade war will cause untold harm to an alliance already in stress and make it harder to rejuvenate the soggy world economy. Cooler heads must prevail.

In Europe, the critical need is to reform the moratorium on GM foods. Frustration over its inability to get the import ban lifted is what pushed Washington to this desperate act. In the US, serious movement in Europe must be seized as pretence to rescind the WTO case before the antagonisms of hearings, judgment, appeal and retaliation unfold.

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.