KOENIGSWINTER, Germany (AP) — Some 40 nations at a high-level climate meeting have made headway toward a pact to curb global warming, but the most important issues remain unresolved, Germany's environment minister said Tuesday.

Many delegates agreed that "this meeting has broken the ice and one cannot overestimate the importance of this," Norbert Roettgen said as the three-day Petersberg Dialogue co-hosted by Germany and Mexico, wrapped up. "This is a contribution to making success possible again."

Progress was made on several issues including saving the planet's forests and transferring climate technology from rich to poor countries, he said.

But the toughest issues — cutting greenhouse gas emissions, financial aid from rich to poor nations, and a method of measuring both — still need consideration, he said.

Chancellor Angela Merkel initiated this meeting of ministers from nations representing all regions of the world at the U.N. climate conference of more than 190 countries in Copenhagen in December.

Copenhagen was originally set to produce an international climate treaty, but it came up only with a political declaration — the so-called Copenhagen Accord brokered by President Barack Obama.

However, the Accord was dismissed by some nations, and the Copenhagen conference ended with a deep rift between industrialized nations, new economic powers China and India, and developing countries — with considerable differences also within each group.

Roettgen said the Petersberg Dialogue, in a mansion high above Koenigswinter near Bonn, had worked to overcome some of the distrust.

"This has proved to be a platform of constructive discussions," he said.

However, a Greenpeace official said the international fight against global warming is still deeply troubled.

"Fundamentally, the difficult situation we had in Copenhagen has not changed," Greenpeace climate specialist Martin Kaiser told The Associated Press.

"The United States still has no climate law, President Obama's climate policies have failed, and therefore there is no basis for an ambitious international treaty that could bring India and China on board," Kaiser said.

Kaiser said the Petersberg Dialogue demonstrated a pragmatic approach, with participants seeking to finalize individual projects to reduce greenhouse gases or help poor countries deal with the consequences of climate change such as droughts, floods, or heavy storms.

"But that won't be enough to make sure greenhouse gas emissions peak by 2015 and go down after that," Kaiser said, referring to a recommendation of scientists on the Intergovernmental Panel on Climate Change.

Outgoing United Nations climate chief Yvo de Boer had said Monday he did not expect the international treaty to be agreed when U.N. negotiators meet in Cancun, Mexico, in December.

Roettgen said Tuesday it remains to be seen how the negotiations will be organized for the rest of the year and if at least parts of the treaty — such as an agreement on saving forests or on technology transfers — can be agreed upon in Cancun.

Roettgen also said Germany does not rule out continuing the Kyoto Protocol after 2012 when its current obligations expire.

In that case, the U.S. and China also "have to deliver" as they are the globe's greatest polluters, he said.

The 1997 Kyoto Protocol obliges industrialized countries to cut their greenhouse gas emissions by 5.2 percent below 1990 levels by 2012. The U.S. has not ratified it, and China and other up-and-coming economic powers are not covered by it.