The UK and California are to work together on reducing greenhouse gases and promoting low carbon technologies.
Tony Blair met Arnold Schwarzenegger in California
The agreement came after a climate change meeting in Long Beach of Tony Blair, the US state's governor Arnold Schwarzenegger and business leaders.
A "mission statement" said the two would, among other things, "share experiences" and "find new solutions".
They would look at whether they could co-operate on an emissions trading scheme, said a spokesman for Mr Blair.
"We are at least on our way to putting in place the framework that will resolve this problem," Mr Blair said in a press conference afterwards.
The meeting - also attended by BP boss Lord Browne and Virgin chief Sir Richard Branson - follows climate change talks between Mr Blair and US President George W Bush at the G8 summit.
The resulting mission statement - signed by both Mr Blair and Mr Schwarzenegger - says Britain and California will "commit to urgent action to reduce greenhouse gas emissions and promote low carbon technologies".
"California and the UK recognise the linkages between climate change, energy security, human health and robust economic growth," it adds.
"Working together, California and the UK commit to build upon current efforts, share experiences, find new solutions and work to educate the public on the need for aggressive action to address climate change and promote energy diversity."
Mr Blair told the meeting: "We know that the answers to this [climate change] will come in the end by the development of the right science and technology.
"This is something that can't be done just by governments doing it.
"We need a joint framework, we need it to incorporate all the main countries in the world and we need not just your commitment but also your expertise."
Mr Schwarzenegger spoke of the private sector and government working together in tackling the issue.
He said: "You can protect the environment and you can make sure the economy grows without any problems - we have shown that here in California."
A spokesman for the British Consulate-General in Los Angeles denied that Britain's pact with California meant Britain was side-stepping the US president.
"That's explicitly not what we are doing," he told Reuters news agency.
Mr Schwarzenegger has put the environment high on his agenda, and backed steps to reduce industrial emissions of greenhouse gases.
Mr Bush withdrew from the Kyoto agreement on global warming in 2001, saying it would cost US jobs, and has favoured a voluntary system to reduce greenhouse gases
Most scientists link emissions such as carbon dioxide from the burning of fossil fuels to global warming.