Prime Minister Tony Blair has welcomed US President George Bush's call for a global warming summit this year but said more was needed.
Mr Blair said a comprehensive global deal was needed
Mr Bush said major polluters needed to set targets and "great breakthroughs" in technology - led by the US - would allow this to happen.
Mr Blair, visiting South Africa, said: "I want to see us now go further from what President Bush laid out."
Climate change and Africa will be key topics at the G8 summit, he said.
Mr Blair has been holding talks with South African President Thabo Mbeki, on the final day of his farewell tour of the continent.
Afterwards, the prime minister said the G8 meeting in Germany had to create "another big step forward" on climate change and the developing world.
All the "main players", including the US, China and India, had to take part, or the world would "be unlikely to make progress", he added.
Mr Blair said: "For the first time America is saying clearly that it wants to be part of a global deal.
"For the first time we have the possibility of a global deal with America in it."
But he added: "Unless everybody is going to understand that we all have a responsibility for this, and step up to the mark and do something, you can have any number of international agreements but they don't deal with the problem."
The US has not signed up to the Kyoto Protocol, which sets out targets on lowering emissions until 2012.
But in a speech on Thursday, Mr Bush said his administration took climate change seriously.
"The United States will work with other nations to establish a new framework on greenhouse gas emissions for when the Kyoto protocol expires," he said.
To achieve this goal, he added, the US would hold a series of meetings bringing together "nations that produced most greenhouse gas emissions, including nations with rapidly growing economies like India and China".
The issue is expected to be top of the agenda when the G8 countries, plus Brazil, China, India, Mexico and South Africa, meet in Heiligendamm, Germany, next week.
Mr Mbeki is seen as the key figure in dealing with the regime of President Robert Mugabe in Zimbabwe.
Mr Blair said: "In the end the solutions to Africa's problems come from within Africa.... In the end, Africa wants to take responsibility for its own destiny and future."
Countries had to address their own problems including corruption and poor governance, while richer nations had to "step up to the plate" on aid.
Mr Blair, who met previous South African leader Nelson Mandela on Thursday, is on his last big trip before stepping down as prime minister.
He hit back at accusations of a "vanity tour", calling UK critics "cynical".
Mr Mandela said he looked forward to welcoming him to "the club of retiring presidents and prime ministers".
Mr Blair will fly back to London later after his four-day final trip to Africa before leaving Downing Street on 27 June.
His tour has also included brief visits to Libya and Sierra Leone.