European governments are lobbying the Bush administration to change course over Iran before next month's presidential election, urging Washington to adopt an incentive-driven policy that Senator John Kerry has already pledged, according to diplomats and US politicians.

President George W. Bush and his Democratic rival agreed in their first election debate on Thursday night that nuclear proliferation posed the most serious threat to US security. But there was clear disagreement over how to stop the suspected weapons programmes of both Iran and North Korea.