UNITED NATIONS - UN Secretary-General Ban Ki-moon on Wednesday commended the efforts made by China and France on climate change after the two pledged in a joint statement to push for solutions to thorny issues that are under negotiations for a universal climate deal.

President Xi Jinping and his French counterpart Francois Hollande issued a joint statement on climate change in Beijing on Monday, vowing to promote a working program to accelerate pre-2020 efforts in mitigation, adaptation and support during the Paris climate summit.

They called for a better transparency system to build trust and confidence in the Paris pact, as well as means to review the actions and support of various parties.

"I commend this and other efforts aimed at finding solutions to the difficult issues under negotiations," said Ban at a high-level event here at UN headquarters on climate change.

Ban also welcomed the agreement between China and France to have a five-year review process to assess and strengthen national commitments to combating climate change over time.

France will host the climate summit in Paris (COP21) in December, which is largely expected to result in a global and binding agreement on addressing climate change.

"The agreement must send a clear signal to the private sector that the low-carbon transformation of the global economy is inevitable, beneficial, and already under way," said Ban.

"It must help accelerate investments in clean energy and spur a global, low-carbon transformation well before the end of the century that is consistent with a below 2 degrees Celsius pathway," he added.

The deadline for a universal climate agreement is just some four weeks away. However, despite months of talks, the key issues still remain in play.

Ban said he will be actively engaging with heads of state and government over the next four weeks to help unlock these issues, while urging countries to make compromise as well as building consensus on matters concerned.