Prime Minister Tony Blair is embarking on a whirlwind tour of world leaders in a bid to win support for his plans for Africa and climate change.
Tony Blair is eager for agreement at the G8 summit
Mr Blair will visit US president George Bush and Russian president Vladimir Putin, Downing Street has said.
Britain's presidency of the G8 is focused on a Gleneagles summit in July.
Mr Blair wants to secure deals on the future of Africa and climate change, but it is not certain he will win the support of his fellow seven leaders.
Earlier this month the BBC learned that the US was unlikely to accept Mr Blair's three-point plan for a new deal on climate change at the summit of industrialised nations.
President Bush's chief climate negotiator Harlan Watson said the science on climate was still uncertain and did not merit urgent action.
Mr Blair and Chancellor Gordon Brown have also placed great emphasis on the UK-led Commission for Africa, with the prime minister saying reducing poverty on the continent was "the fundamental challenge of our generation".
The official spokesman for Mr Blair said: "We have set out an ambitious agenda for the G8 and this is the time for detailed negotiation.
Blair and Bush will talk some more
"The important point is that no one in the G8 disputes that Africa and climate change must be priorities. We believe at this stage we are achieving progress, but we still have some way to go."
Mr Blair plans to meet all seven leaders ahead of the G8, beginning with his Italian counterpart Silvio Berlusconi in Rome on Friday.
He visits Moscow and Washington next month, and will also see French president Jacques Chirac and German Chancellor Gerhard Schroeder. He will speak to his colleagues in Canada and Japan by video conference link.
Mr Blair wants G8 countries to agree a debt relief package for Africa, and to boost economic reform and good governance.
And Putin can expect a visit too
His spokesman said: "In terms of various countries' position, all I would stress is that this is a proper negotiation and when you are driving a proper negotiation it's generally counter-productive to comment on the positions of other countries.
"People will not take up final positions at this stage."
The issues will also feature at the United Nations Millennium Summit in New York in the autumn, and the next World Trade Organisation meeting in Hong Kong in December.
"The G8 is a major point in that process and we are going for it," added the spokesman.
Britain took on the Presidency of the G8 at the start of the year, and the annual summit will be at the Gleneagles Hotel in Scotland from 6-8 July.
At Gleneagles, construction work has begun on a five-mile wire mesh cordon to keep protesters from disrupting the summit.
Tayside Police Assistant Chief Constable Willie Bald said the fence was one of several security measures being taken to secure the event.
"It clearly outlines the secure boundary lines which will be policed and
where powers of arrest can be used if anyone attempts to get through," he said.