Recession is set to cause the sharpest fall in world greenhouse gas emissions in 40 years, according to an estimate yesterday as world leaders gather in New York to try to break deadlock on a new climate treaty.

The International Energy Agency (IEA) said output of carbon dioxide, the commonest greenhouse gas from burning fossil fuels, would fall by about 2.6 percent this year worldwide amid a tumble in industrial activity.

It expressed hopes that the world would seize on the decline to shift to lower-carbon growth despite worries that governments might take it as an excuse for inaction.

"This fall in emissions and in investment in fossil fuels will only have meaning with agreement in Copenhagen which provides a low-carbon signal to investors," IEA chief economist Fatih Birol said.

World leaders are to meet at UN headquarters in New York today for a one-day climate summit to try to unlock 190-nation negotiations on a new deal to combat global warming due to be agreed in Copenhagen in December.

Negotiations among 190 nations are stalled over how to share out curbs to 2020 between rich and poor and on how to raise perhaps US$100 billion a year to help the poor combat warming and adapt to changes such as rising seas or desertification.

Some experts expressed doubts that recession and falling industrial output could be a springboard to greener growth.

"When politicians talk about the financial crisis everything is about returning to growth, which means higher emissions," said Paal Prestrud, director of the Center for International Climate and Environmental Research in Oslo.

"We have to reduce emissions in a planned way to avoid social problems, not through recession," he said.

The UN talks are "dangerously close to deadlock", European Commission President Jose Manuel Barroso was due to say later yesterday and challenge developing nations to do more in order to secure financial support from industrialized nations.

"This may not be a simple negotiating stand-off that we can fix next year," according to notes for a speech in New York. "It risks being an acrimonious collapse, delaying action against climate change perhaps for years."