Mr Blair signed the statement of intent yesterday with California's governor Arnold Schwarzenegger, saying it would lay the groundwork for a new transatlantic market in carbon dioxide emissions. The prime minister wants to create a coalition of the willing among those US states prepared to join the European Union's carbon trading scheme, which sets country-by-country overall caps for carbon, and rewards individual companies which find a profitable way to minimize carbon emissions.

With other US states also interested or involved in carbon trading markets, the path is being opened to bring US business into international efforts to fight climate change, even though international progress has been stymied by the Bush administration's refusal to sign up to binding targets in the Kyoto protocol.