More than 30 Canadian internet pharmacies have decided not to accept bulk orders of prescription drugs from US states and municipalities. The move delivers a potentially serious setback to US politicians - most notably Democratic presidential candidate John Kerry - campaigning to give Americans easier access to cheap drugs from Canada.

Mr Kerry has argued that opening the US to Canadian imports could help lower the costs of prescription drugs for elderly Americans. Such reimportation has become one of the points of difference between him and President George W. Bush during the election campaign.