China said on Thursday it will not bow to pressure to rethink a key climate change treaty and was preparing to cope with a "gap" in the pact after 2012 if rich nations fail to add new greenhouse gas goals in time.

Envoys from 177 governments are holding week-long talks in the northern Chinese city of Tianjin on the shape of a successor pact to the Kyoto Protocol, the U.N.'s main weapon in the fight against climate change.

Kyoto's first phase, which binds about 40 rich nations to meet emissions targets, expires in 2012 and there's no clarity on what happens after that, worrying investors in clean-energy projects who want long-term certainty on climate policies and financing.

"Of course, now we're discussing the legal issues if it happens," said Su Wei, a senior Chinese climate change negotiator, referring to a possible gap in Kyoto.

"I think that from a practical angle that is necessary, but it seems a bit early, prejudging the negotiations," he added.

The United Nations has been stepping up efforts to convince countries to avoid a gap after 2012 and to ensure certainty for the U.N.'s $2.7 billion carbon market that is part of Kyoto.

But the bitter negotiations are largely stalled over lack of trust between rich and poor nations, particularly over the issue of how to share the burden in emissions cuts to avoid dangerous climate change, which scientists say could trigger more extreme weather, crop failures and much higher sea levels.

Nearly all wealthy countries have signed up to legally binding emissions goals under Kyoto, with the big exception of the United States, which refused to become a party.

Developing nations, including the world's top carbon emitter China, are only obliged to take voluntary steps to curb the growth of their emissions.

The United States and other rich nations want a new global pact to do away with that either-or division to reflect the surge in emissions from the developing world, which is now responsible for more than half of mankind's annual greenhouse gas emissions.

PLAYING CHICKEN

Rich nations also want China, India, Brazil and other big emitters to agree to make their voluntary emissions reduction efforts legally binding, regularly reported and verifiable.

Su told Reuters his government would not bend to Western demands and was reluctantly thinking about how to handle the likelihood that the first phase of Kyoto could expire with no full legal extension to replace it.

It also exposes game of "chicken" between rich economies and emerging powers that could trouble higher level negotiations in Cancun, Mexico, in less than two months that are intended to lay the foundations for a new, legally binding climate deal.

Su said rich nations were to blame for failing to offer make greenhouse gas vows for Kyoto in time to ensure a seamless extension of the agreement from 2013.

"The developed countries are delaying and delaying," he said.

"Even if Cancun makes no decision on the developed countries' emission targets in the second phase (of Kyoto), then after Cancun we'll accelerate the process. I think that at the most we can't delay it beyond a year."

Negotiations last year failed to agree on a binding treaty and climaxed in a bitter meeting in Copenhagen, which produced a non-binding accord that later recorded the emissions pledges of participant countries.

The question now is whether those pledges are formalized under Kyoto or under a new treaty. The United States is pushing China and other powers to jump aboard a proposed new pact built on the Copenhagen Accord.