"Almost 100 per cent of our agricultural exports in the next five years will be genetically modified or combined with bulk commodities that are genetically modified," he said in congressional testimony.
His warnings came after European Union environment ministers agreed a de facto moratorium on GM foods. The US is gearing up for a pitched battle with Europe, as the EU hardens its position and new world trade talks approach.
Dan Glickman, the US Agriculture Secretary, warned last week that GM foods would be a "make or break" issue in world trade talks due to start in Seattle later this year. Europe's attitude "has disrupted trade and threatens to constrain innovation in one of the most promising new technologies for ensuring future global food security", he said.
"Countries cannot be free to independently develop ad hoc policies based on questionable science. That will lead to trade chaos and thwart progress for agricultural issues in the next [world trade] round."
Charlene Barshefsky, US trade representative at the World Trade Organisation, said American farmers "must not suffer trade discrimination as a result of adopting scientifically proven techniques".
The EU proposal, which needs to be formally approved by the European Parliament, would end permanent authorisation for GM seeds. Instead, there would be only temporary approvals, as well as tougher labelling and monitoring.
"If any evidence does arise of risk to human health or environment, approval can be withdrawn," said the Environment minister, Michael Meacher.
"No one can now and in the future seriously argue that the regulatory procedures are not tight, comprehensive and balanced and in my opinion very effective," Mr Meacher said.
In practice, no new GM seeds are likely to be approved before 2002, when a new law is expected to be in operation.
"This decision has serious implications for Europe and in the world market and ministers know it," Benedikt Haerlin, a Greenpeace co-ordinator, said.