Envoys from the 20 countries, whose greenhouse gas emissions account for about 80 percent of the global total, wrapped up two days of talks hoping to jumpstart negotiations on a successor to the Kyoto Protocol.

"We reconfirmed the principle of common but differentiated responsibility in negotiating the next deal for 2013 and onward," said Japan's environment minister Ichiro Kamoshita, the meeting's co-chair.

"It was made clear that there are a variety of positions among developed countries, emerging countries and developing countries," Kamoshita told a news conference after talks ended.

Developing countries have insisted that they not be held up to the same targets as wealthy nations in reducing greenhouse gas emissions blamed for global warming.

There are also disagreements among rich nations. The United States has shunned the Kyoto Protocol, whose obligations end in 2012, saying it is unfair by making no demands of developing nations.

Japan in July hosts the Group of Eight summit of rich nations which it hopes will make progress in the UN-backed goal of drafting Kyoto's successor by the end of next year.

"Japan's role as the (G8) host will be how to coordinate these opinions. And I think what's important is how Japan can send a message that strengthening support to developing countries is important," Kamoshita said.

"Also important is how the G8 members can go further to achieve our current emission cuts targets, and what we can do to realise the long-term goal of halving the global emission by 2050," he added.

Last year's G8 summit in Germany said rich nations would "seriously consider" slashing emissions by half by 2050. But there was no binding commitment and the base year was vague.