SHANGHAI--A new pledge by China to show "the highest possible ambition" in the fight against climate change could see the world's biggest greenhouse gas emitter introduce new and more stringent carbon targets next year, according to experts and policy advisors.

As U.S. President Donald Trump continues to cast doubt on the reality of climate change, China is becoming a crucial driving force behind worldwide initiatives to combat global warming, especially ahead of a United Nations summit in New York in September.

In a statement issued on the sidelines of the Group of 20 summit in Osaka on Saturday, China's top diplomat State Councillor Wang Yi, French Foreign Minister Jean-Yves Le Drian, and United Nations Secretary General Antonio Guterres vowed to "scale up efforts to tackle the climate and biodiversity crisis."

China and France also pledged to "update" their contributions beyond their current ones to reflect "their highest possible ambition." The 2015 Paris climate agreement encourages countries to make stronger pledges if they are able to do so.

"I believe this is the first time the Chinese government has officially talked about updating their nationally determined contributions," said Zou Ji, president of the Energy Foundation in Beijing and a former member of China's climate negotiating team.

Li Shuo, senior climate adviser with environmental group Greenpeace, said the commitment to "update" rather than reaffirm current contributions also suggests that stronger pledges will be made.

"'Highest possible ambition' can't be there if there is no desire at all from Beijing," he said.

"I think (Chinese leaders) get the idea that they need to enhance their ambition, not only for their image as international climate leaders but also for larger geopolitical reasons, such as supporting multilateralism."

The statement by China, France and the UN also acknowledged the importance of achieving net zero carbon dioxide emissions by balancing CO2 sources with "sinks" that lock up greenhouse gas, but it stopped short of setting a target date. Europe is pushing for China to issue a 2050 pledge.

China aims to bring emissions to a peak by "around 2030" and raise the share of non-fossil fuels in its total energy mix to 20 percent by the end of the next decade, up from 15 percent in 2020.

China's Ministry of the Environment and Ecology did not respond to a request for comment. However, the China Council for International Cooperation on Environment and Development (CCICED), a government think tank, is advising Beijing to introduce more stringent climate targets in its next five-year plan.

The CCICED called last month for China to bring emissions to a peak by 2025, raise the share of non-fossil fuels in the energy mix to 25 percent by 2030 and to achieve carbon neutrality by 2060-2070.

"It is very challenging but China still has a lot of room to improve and it should regard it as part of its own process of modernization," said Zou, who was involved in drawing up the CCICED recommendations.