This summit would focus on the hunt for a successor to the Kyoto Protocol on cutting greenhouse gases widely blamed for forecasts of more heatwaves, floods, droughts and rising sea levels.

UN environment agencies are lobbying Ban to play a leading role in helping governments battle climate change after Kyoto expires in 2012. But he stopped short recently of endorsing his officials? proposal for a summit of some 20 key leaders.

?I know the Kenyan government has proposed to have such a summit. I?m going to discuss that with the president (Kenya?s Mwai Kibaki),? he said during a visit to a Nairobi slum.

?Climate change is one of the most important issues that the international community must address before 2012. I will work very closely with members of the United Nations to discuss this,? he told reporters.

In New York, Ban Ki-moon?s chief spokeswoman, Michele Montas, said the UN secretary-general remained undecided on whether to push for a climate summit, as recommended by UN Environment Program Executive Director Achim Steiner and Yvo de Boer, head of the UN Climate Secretariat.

Climate change remained among Ban?s top priorities but there was no decision to go ahead with a summit and no date yet set for such a meeting, Montas said.

Last week, the broadest scientific study of the human effect on the climate is set to conclude there is at least a 90 percent chance that human activities, mainly burning fossil fuels, are to blame for most of the warming in the last 50 years.

In a previous report in 2001, the Intergovernmental Panel on Climate Change (IPCC) said the link was at least 66 percent certain. IPCC experts are meeting in Paris to discuss and approve the draft report.

The report is also set to warn that average global temperatures will rise to 2.0 to 4.5 degrees Celsius (3.6 to 8.1 Fahrenheit) above pre-industrial levels by 2100, with a ?best estimate? of a 3.0 C (5.4 F) rise, scientists say.

Another section of the report, due in April, is expected to warn that between 1.1 and 3.2 billion people will face water shortages by the end of the century and hundreds of millions will go hungry, according to Australia?s The Age newspaper.

De Boer has said the new secretary-general would be in an excellent position to help step up action on climate change, but would first have to assess whether he had enough political support to fulfil the role.

Under Kyoto, 35 industrial nations agreed to cut carbon dioxide emissions by 5 percent below 1990 levels by 2008-12.

Washington pulled out in 2001, arguing it cost jobs and wrongly excluded poorer nations. President Bush last week called climate change a ?serious challenge.?

The biggest challenge of the post-Kyoto era is to entice non-participants like the United States, China, India, South Africa and Brazil to join to make the process more effective.

The last annual UN meeting of about 100 environment ministers in Nairobi in November made little progress on finding ways to broaden the protocol after it runs out.