OSLO (Reuters) — Climate talks by the Group of 20 and a suggested shift to majority voting for UN decisions could revive work on a new pact to fight global warming after the low-ambition Copenhagen summit, analysts say.

The UN Climate Change Secretariat has asked all nations for views by February 16 about how many UN meetings are needed in 2010 to try to build momentum for the next annual ministerial talks, in Mexico from November 29 to December 10.

Countries are unclear what to do after Copenhagen fell short of a binding treaty urged by most nations and left the 2010 calendar almost bare. The only other planned UN meeting before Mexico is of bureaucrats, in Bonn from May 31-June 11.

"So far there hasn't yet been the engagement of a smaller group of countries to lead the way," said Jennifer Morgan, director of the World Resources Institute's climate and energy programme.

Analysts said the G20, with summits in Canada in June and South Korea in November, might be able to help by focusing more on climate change. Calls for a relaxation of a need for unanimity on key UN decisions could ease work on a new deal.

"We need to work on the UN process — item one is to allow for majority decisions," said Johan Rockstrom, head of the Stockholm Resilience Center at Stockholm University.

All agree that the 194-nation UN talks are unwieldy so smaller groups are needed along the way. But Copenhagen showed that developing nations — including those most vulnerable to desertification, rising sea levels or floods — felt left out.

This year, US President Barack Obama might want to defer to the G20 rather than push the U.S.-led Major Economies Forum (MEF) of 17 top emitters, which met six times in 2010. The G20 adds Argentina, Saudi Arabia and Turkey to MEF members.

"The United States will be very careful not to set up something that looks like a rival process to the UN," said Alden Meyer, of the Union of Concerned Scientists, adding that the G20 was a more likely venue than the MEF for climate talks.

Washington is an outsider among rich nations by staying out of the UN's existing Kyoto Protocol for cutting emissions by 2012. And carbon capping legislation is stalled in the Senate.

Robert Stavins, director of the Harvard Environmental Economics Program, also said Washington might be more willing to favour the G20 than the MEF. The MEF might meet if other countries, perhaps the European Union, asked for talks.

December's Copenhagen summit disappointed many nations with a deal led by major emitters such as China and the United States to limit global warming to below two degrees Celsius (3.6 F), twinned with a promise of $100 billion in annual aid from 2020.

Stavins said that finding a path to a more robust deal was a "tremendous challenge".

"It's also a game of chicken between the United States and China: China is not going to take action before the US does. The US Congress is very reticent to take action unless China does," he said.

Mexican President Felipe Calderon has urged a review of the principle of unanimity to streamline decisions.

The Copenhagen Accord, the main outcome of the summit, was merely "noted" rather than "adopted" as a UN plan after opposition from Sudan, Cuba, Nicaragua, Venezuela and Bolivia.

"It's tempting to hit on the UN and its inability to deal with (climate change). My personal take on this is that the UN is the only one which can take us to a global agreement," Rockstrom said.

"We've done it before under the Montreal Protocol," he said, referring to the 1987 pact for protecting the ozone layer.