Xie Zhenhua says Trump's decision to withdraw from the Paris deal hurt the confidence of many other countries, but its impact is now beginning to wane

* Envoy says China's commitments are unbending

* Impact of Trump withdrawal from Paris accord is waning

* Urges developed countries to work to implement Paris deal (Adds detail, background)

By Christian Shepherd

BEIJING, Nov 26 (Reuters) - China will work to achieve its existing greenhouse gas targets and strive to do better as the challenges of climate change become more urgent, Xie Zhenhua, the country's top climate envoy, said at a briefing on Monday.

"I believe the promises we make will be 100 percent completed and we will strive to do better," said Xie, speaking to reporters before a new round of climate talks in Katowice, Poland on how to implement the 2015 Paris agreement.

"Although we have encountered a lot of difficulties, a lot of problems, our targets and our resolution will not change," he added.

China, the world's biggest source of climate-warming carbon dioxide, has pledged to halt its rise in emissions by "around 2030" through cleaner forms of energy, boosting efficiency and encouraging high-technology industries.

However, overseas researchers have suggested that China's emissions already reached a peak of 9.53 gigatonnes in 2013 and declined in the three years that followed, suggesting that Beijing's targets were far too conservative.

U.S. President Donald Trump said last year that he would pull out of the 2015 agreement, arguing that it was too lenient on China.

Xie said Trump's decision to withdraw hurt the confidence and resolution of many other countries, but its impact was now beginning to wane, and China's own commitments to clean, low-carbon development were unbending.

China has already met a target to cut carbon intensity - the amount of CO2 emissions per unit of economic growth - by 40-45 percent from 2005 levels by 2020, and it is also on course to bring the share of non-fossil fuels to 15 percent of total energy consumption by the end of the decade, Xie said.

China was the world's biggest investor in renewable energy and is in the process of establishing the world's largest carbon trading exchange, he added.

Xie said he hoped developed countries would honour their commitments to the Paris agreement and provide the promised financial and technical support to poorer nations.

He also called on nations to use the upcoming G20 meeting to reaffirm their commitment to combating climate change.

"We hope that this meeting can send out a strong political signal that these economic powers should continue to make efforts to carry out the Paris Agreement and 2030 sustainable development goals," Xie said. (Reporting by Christian Shepherd; writing by David Stanway;editing by Darren Schuettler and Richard Pullin)

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