The goal of annually mobilizing 100 billion dollars by 2020 to battle global warming may be challenging but feasible, UN Secretary General Ban Ki-moon said Wednesday.

"Climate financing is one of the most important aspects of our efforts to address the climate change challenge," Ban said at a side meeting of the U.N. climate conference in Cancun, Mexico.

It is crucial for the climate program to catalyze the efforts for developing countries and for building trust between developing and developed nations, Ban said.

The UN leader urged the gathering to make extra efforts to identify new, innovative and additional sources for long-term financing.

The financing would help developing nations buy advanced clean-energy technology to reduce their own emissions, and to adapt to climate change, such as building sea walls against rising seas and upgrading farming practices to compensate for shifting rain patterns.

Despite failing to agree on a legally binding climate deal last December in Copenhagen, industrialized countries set a goal of mobilizing 30 billion U.S. dollars by 2012 as fast-start funding and 100 billion dollars per year by 2020 as long-term funding to support adaptation and mitigation in developing countries.

Ban stepped into the middle of the debate earlier this year by enlisting a high-level group of international political and financial leaders to offer advice.

On Wednesday, Ban presented the group's ideas to the conference, including airline and foreign-exchange levies, as he led a discussion with key figures on the panel.

The group studies potential sources of revenue that will enable climate change financing promised during the Copenhagen summit. It also develops proposals on how to increase long-term financing from public and private sources.

The annual meeting of parties to the 193-nation UN climate treaty, running from Nov. 29 to Dec. 10 in this Mexican resort city, aims at finding solutions to global climate change.