China on Wednesday issued its first ever absolute targets for cutting planet-warming gases, as the United States doubles down on fossil fuels.

The announcement was delivered via video by President Xi Jinping to a UN climate summit where some 120 nations will outline plans to curb global warming.

Under the new plan, China will reduce economy-wide greenhouse gas emissions by 7 to 10 percent by 2035, from peak levels.

These targets represent China's best efforts based on the requirements of the Paris Agreement, Xi said, adding that meeting these targets requires both painstaking efforts by China itself and a supportive and open international environment.

He also stressed China has the resolve and confidence to deliver on its commitments.

"Green and low carbon transition is the trend of our time," Xi said. "While some country is acting against it, the international community should stay focused in the right direction."

The summit comes a day after US President Donald Trump used his UN General Assembly speech to blast climate change as a "con job" and criticise countries for embracing renewable energy technologies.

UN Secretary General Antonito Guterres hosted the climate leaders’ summit on the sidelines of the UN General Assembly.

He asked countries to announce their new climate targets to drum up momentum for the global COP30 climate negotiations in November. (Xinhua/AFP)