Time is running out for China to deliver its U.N. submission in the first half of this year, as it has said it will do.

Once China, the world's biggest emitter, has submitted its so-called Intended Nationally Determined Contribution (INDC) ahead of U.N. climate talks in Paris late this year, pledges submitted will cover more than half the world's emissions.

"We will make strenuous efforts to address climate change," Li said in Brussels. "By the end of this month, the Chinese side will submit to the U.N. secretariat on climate change our Intended Nationally Determined Contribution plan."

The European Union, whose member state France will host the Paris climate change talks beginning on Nov. 30, is anxious to avoid a repeat of the failed Copenhagen U.N. summit in 2009, the last attempt to reach a global climate deal.

That summit foundered partly because of Chinese reluctance to make binding commitments.

This time around, China is adopting a markedly different stance. It still categorises itself as a developing economy with challenges, but is backing EU efforts to curb emissions and recognises the need to develop sustainably.

Speaking at a conference in Brussels, Li said the EU and China must "step up their cooperation ... to establish a fair, reasonable, win-win global climate governance system."

Also on Monday, Xie Zhenhua, China's special representative on climate change, addressed a high-level U.N. panel in New York. He said China was a developing country but had an "inherent need for sustainable development".

China's pledge is expected to be a promise that its emissions will peak "around 2030", which officials and analysts said it can easily achieve.

"The INDCs should be seen as a floor not a ceiling," Marianne Fay, chief economist for climate change at the World Bank, said in Brussels. "China likes to under-promise and over-deliver."