Prime Minister Tony Blair has held talks with German Chancellor Angela Merkel in Berlin ahead of this week's G8 summit.
Tony Blair said Africa would be a crucial topic at the summit
At a press conference after the meeting, Mr Blair welcomed a US commitment to become part of a global agreement on climate change.
He also said a critical topic would be Africa and sticking to commitments made in 2005 at the Gleneagles G8 summit.
This week's gathering will take place in Heiligendamm on Wednesday.
Mr Blair wants a framework to be drawn up with the "plus five" states - China, India, South Africa, Brazil and Mexico - for action to tackle global warming, to replace the Kyoto targets for reducing greenhouse gas emissions, which expire in 2013.
US President George W Bush has announced his own climate strategy raising the prospect of a showdown with the European nations at the G8 summit.
Mr Bush called for a separate international gathering to create a "new global framework" on the issue in the autumn, rejecting the European approach to cutting greenhouse gases in favour of a technology-led model.
At the press conference Mr Blair said the US announcement was a positive step.
He said: "I think a sensible analysis would say that it is good that the United States has committed to being part of a global agreement, and has committed to the goal of a substantial reduction in emissions.
"These are commitments that have not been made before, they're made now - that's important.
"However, we then need to go further. We need to make sure that we set a clear global target."
He said it was also crucial to continue with commitments made on Africa at the G8 meeting in Scotland two years ago, when Britain had presidency of the organisation.
He said he had seen progress being made in providing HIV/Aids treatment while on a trip to Africa last week.
He said: "People were telling me, experts from Africa, we would save millions of lives over the next few years just on that one commitment alone.
"And it's an indication of why it's so important that when we are able to act we do act."
The German chancellor has put climate change and Africa at the top of the agenda for her presidency of the G8.
The G8 nations - Britain, the US, Germany, France, Italy, Japan, Canada and Russia - are under pressure to make good on promises made at Gleneagles to double aid and write off debts.
They are expected to confirm their intention to implement pledges made at 2005's Gleneagles summit for an extra $50bn in annual aid by 2010.
Mrs Merkel was reportedly to warn Mr Blair she wants to revive the stalled European constitution at their meeting
She will push ahead with the plan at an EU summit in Brussels on 21 June.
The German chancellor, who currently holds the presidency of the EU, wants a wide-ranging treaty to take forward many of the proposals in the constitution rejected by French and Dutch voters two years ago.
But - at what will be his final major engagement before stepping down as prime minister - Mr Blair will push for a scaled-down treaty to update the EU's institutions without the wider and more controversial constitutional elements.