BEGINNINGS have been more auspicious. The roughly 150 European and American trade negotiators who are due to start work on the Trans-Atlantic Trade and Investment Partnership (TTIP) in Washington, DC, on July 8th will do so in the wake of reports that America’s intelligence dragnet targeted European Union officials. In the ensuing uproar François Hollande, the president of France, suggested that TTIP talks should be delayed until questions about the spying allegations were answered. That idea seems to have been ditched. But the risk that one of the biggest trade deals in decades could be derailed by mistrust or bickering has been underlined.

Together America and the EU account for around $30 trillion in annual output, almost half the world total. Freer exchange between them could boost global GDP by 0.6% a year, or more if knock-on effects on productivity are included. The impact would be bigger still if a TTIP deal spurred multilateral efforts to cut trade barriers.

A comprehensive agreement that includes non-tariff barriers (NTBs) would be especially enticing. Post-war trade liberalisation has mostly meant slashing tariff rates. Duties between America and Europe are low already. More cuts wouldn’t hurt, but NTBs are the biggest hurdles to trade.

These non-tariff obstacles include outright discriminatory measures like import quotas and the sort of “Buy American” government-purchasing rules so beloved of politicians. But they also include basic regulatory standards. Separate drug-approval processes in Europe and America add to the burden of operating across the Atlantic, for example. Different consumer-product safety standards or inspection procedures have similar effects. Common standards, or mutual recognition of each other’s regulatory processes, could deliver an economic boost.

The Centre for Economic Policy Research (CEPR), a think-tank in London, reckons that current NTBs are far more burdensome than tariffs. Chemical exporters to America face a tariff rate of 1.2%, for example, and non-tariff barriers equivalent to a 19.1% duty. European NTBs add what amounts to an additional 25.5% duty on top of the 8% tariff already levied on American car imports.

An ambitious trade deal would therefore produce big benefits. CEPR suggests an agreement that eliminates all remaining tariffs and cuts NTB costs by 25% would lift annual EU output by roughly 0.9% and American GDP by 0.8% (see chart). Annual exports for each economy could rise by nearly 2% of GDP. A less ambitious deal that left some tariffs in place and cut NTB costs by 10% would yield gains around half that size. One that only slashed tariffs would bring gains less than a fifth of those for a comprehensive deal. Achieving a broader agreement will not be easy. Both sides have well-known sensitivities. Europeans are prickly about American agricultural practices, like the use of genetically modified foods. Americans will cling to carve-outs for domestic shipping and transport firms. The recent revelations about American espionage activities may complicate discussions on data-protection standards. Political leaders have tried to keep the scope of talks as wide as possible, leaving maximum room for compromise and consensus. That strategy has already encountered hiccups. France refused to support giving a mandate to EU negotiators until it had secured protection for “cultural diversity”—code for subsidies to the French film industry. But, in an encouraging sign for the discussions to come, the French position drew scorn from normally sympathetic EU members and restraint from American officials and interest groups. The opening round of talks in Washington are designed to craft an agenda that offers the best chance of a comprehensive deal. Early discussions will focus on things like the sequencing of topics—tariffs must wait, for example, until America concludes an impact study later this year—and the frequency of meetings. The wrangling proper may only start in the autumn.

An agreement by November 2014 remains the target, although given the technical nature of the issues, with teams of regulators niggling over thousands of topics, talks may stretch into 2015. The important thing will be to maintain a sense of haste. Trade talks rarely improve with age. The prize on offer is a grand one; now it’s up to the negotiators to grab it.