Last year, Washington filed a WTO suit against the EU's unofficial moratorium on genetically-modified (GM) crop approvals, claiming its farmers were losing $300 million a year in sales.

Since then, Brussels has put in place new labeling and traceability requirements for GM crops that Byrne said would allow authorizations to resume soon.

The first to be approved is an engineered sweet maize variety known as Bt-11, marketed by Swiss agrochemicals giant Syngenta, Byrne said following two days of meetings with U.S. agriculture and trade officials.

The EU will approve a second variety, a herbicide-resistant maize type known as NK603 sold by the U.S. life sciences firm Monsanto, in the weeks after, he said.

Once authorizations resume, "I would expect the (WTO) case to fall away, in one way or another," he added.

However, Washington has been considering challenging the EU's labeling and traceability requirements at the WTO because of complaints from U.S. farm and agribusiness groups that the new system is an unworkable and costly burden.

Byrne said he urged U.S. government and industry officials to give the labeling and traceability program a chance to prove itself before bringing a case.

He noted the law will be up for review in two years and could be adjusted then to address concerns. "I think that's the best way forward in this case," Byrne said.

David Hegwood, a U.S. Agriculture Department trade adviser, said the Bush administration had not decided whether to challenge the labeling and traceability scheme at the WTO.

"We raised our concerns about the feasibility of implementing what they've proposed and the concerns that we've been hearing," he told Reuters after Byrne met Wednesday with U.S. Agriculture Secretary Ann Veneman.