Commitments by most developed countries to cut carbon emissions are likely to expire at the end of next year without a new round of legally binding pledges, the UN's climate chief warned Monday.
Christiana Figueres said governments needed to start preparing for a gap on the expiry of pledges under the Kyoto Protocol, which has formed the foundation of the world's efforts to cut the emissions that are blamed for global warming.
"Governments have to face the fact that a gap in this effort looks increasingly impossible to avoid," Figueres told reporters in Bangkok during the UN's first round of climate talks for the year.
"In 2011 they need to figure out how to address this issue and how to take it forward in a collective and inclusive way. Resolving this will create a firmer foundation for an even greater collective ambition to cut emissions."
Signed in 1997, the Kyoto Protocol saw most developed nations agree to legally binding agreements in curbing their greenhouse gas emissions.
Those commitments are due to expire at the end of 2012.
But Japan and Russia have firmly opposed extending the protocol because it excludes the world's two biggest polluters -- China and the United States -- and therefore only covers about 30 percent of global emissions.
China did not have to commit to cutting emissions because of its status as a developing country, while the United States refused to ratify the protocol.
Japanese delegates to the Bangkok talks said their country would hold firm in its opposition to signing up for a second phase of emission reduction commitments unless the United States and China did the same.
"We will not change our position. We don't change, we haven't changed, we will not change," the deputy director general for global issues with Japan's foreign affairs ministry, Akira Yamada, said in an interview with AFP.
Some governments and many observers have warned that failing to reach an agreement on fresh carbon emission reduction targets would undermine potential progress in other vital areas of the UN's efforts to tackle global warming.
But Figueres said the Kyoto Protocol would not necessarily collapse without the legally binding commitments, and that countries could continue with other important elements.
"There are many different components of the Kyoto Protocol and they have the possibilities of deciding which of those, and all of those if they wish, would continue to operate," she said.
"For example the market mechanisms, for example the compliance system, the rules-based approach of the Kyoto Protocol.
"All of those are very important parts of the Kyoto Protocol that parties are free to choose which ones of those they want to continue and in what form."
The Japanese delegation in Bangkok also insisted UN efforts to combat climate change need not falter, and the Kyoto Protocol could remain effective, without a new round of legally binding emission cut pledges in time for 2013.
This could be done by implementing agreements on a wide range of long-term climate actions made by all countries at the last annual UN climate summit in the Mexican resort of Cancun in December, Japanese delegate Jun Amira said.
"Our first priority is how to operationalise the Cancun agreement," Amira told AFP.
The Cancun accord saw all 194 parties to the UN's Framework Convention on Climate Change pledge "urgent action" to keep temperatures from rising no more than two degrees Celsius (3.6 Fahrenheit) above pre-industrial levels.
The six days of talks in Bangkok, which began on Sunday, are aimed at kickstarting UN negotiations for the year ahead of the world body's next annual climate summit in Durban, South Africa, in November.
Explore further: Five anthropogenic factors that will radically alter northern forests in 50 years