The European Commission is taking up complaints from online gambling operators that US gambling laws are being targeted at European companies to protect certain US operators, such as the websites run by the US horse-betting industry.
But in a letter responding to formal Commission questions, Susan Schwab, the US trade representative, said there was "no basis for any allegation of 'discriminatory enforcement' of US gambling laws".
The dispute is likely to escalate next month when Peter Mandelson, EU trade commissioner, sends a delegation to Washington to press its case with US lawmakers and hold a press conference.