Routes to Heiligendamm in Germany shut after a day of violent protests in Rostock.
“We’ve not sat down with China, India, Brazil, Mexico, South Africa,” he said.
G8 leaders start their annual summit in the Baltic resort of Heiligendamm later on Wednesday.
Their representatives have been holding weeks of talks on climate and other agenda items.
Combatting climate change is the number one objective set by Angela Merkel, the German chancellor, the G8 host.
Chancellor Merkel has called on G8 leaders to give the fight against climate change a new direction.
“The accelerated climate change is a serious threat,” Merkel wrote in Der Tagesspiegel newspaper. “If we don’t stop it, it will lead to massive environmental problems and increased economic burdens. Therefore, we need decisive action from the international community.
“In Heiligendamm we want to give impetus to the negotiations on global climate protection.
“I hope there will be a signal from Heiligendamm that the countries represented there clearly recognise their collective responsibility.”
Merkel has staked Germany‘s presidency of the G8 on persuading her counterparts to agree to limit the global temperature rise to two degrees Celsius and to cut greenhouse gas emissions by 50 per cent compared with 1990 levels by 2050.
The German plan has won qualified support from some G8 nations, but Merkel faces opposition from the US which is opposed to mandatory emissions limits.
Merkel said helping the poor and developing African economies were other priorities of the three days of talks to which the leaders of emerging nations including South Africa are also invited.
The chancellor said she wanted the meeting to “give globalisation a human face” and said she hoped protests against the summit would be peaceful.
Hundreds of police have been injured in four days of clashes in protests in the nearby northeastern city of Rostock.
About 16,000 police will be on duty for the summit.