WARSAW, Poland (AP) — The global financial crisis will make it harder for countries to agree on an ambitious new treaty to combat global warming and underscores the need to make green technologies profitable, the U.N. climate chief said Thursday.

"Climate change is an environmental problem looking for an economic answer," Yvo de Boer said at a news conference in Warsaw. "The challenge...is to achieve green economic growth."

De Boer spoke ahead of a major two-week climate change conference that begins Monday in Poznan, Poland. Participants from more than 190 countries will work out the details of a climate change accord to succeed the Kyoto Protocol that expires in 2012.

"The financial crisis will throw a shadow over the climate change negotiations," said de Boer, executive director of the United Nations Framework Convention on Climate Change. "That is why I put so much emphasis on the climate regime becoming self-financing."

Citing an example, he said that could involve the auctioning of CO2 emission rights in industrialized countries.

De Boer said a worldwide financial slump will lead initially to lower emissions of carbon-rich gases as economic activity slows down. But the overall impact is damaging because the slowdown will hurt the world's poorest people more than anyone else.

Lower oil prices also will make investing in green energy projects less attractive. And the pool of investment capital available to fund them already has shrunk.

De Boer cited a 2006 report by British economist Nicholas Stern, which warned that if the world does not act to halt global warming, it will cause an economic catastrophe on the scale of the two world wars and the Great Depression combined.

"I hope the financial crisis will not lead to a choice for cheap and dirty technologies because in both the energy sector and in industry those technologies have a lifetime of 30 to 50 years," de Boer said.

The Poznan conference marks a key step in the search for a deal to succeed the Kyoto Protocol, which is expected to be signed in Copenhagen at the end of 2009.

De Boer spoke at a two-day conference of government officials and representatives of some of the most polluting industries — steel, aluminum and concrete — in order to include them in the push to cut greenhouse gas emissions.