A one-sentence note from China's top climate change negotiator, Su Wei, authorized the addition of China to the list attached to the non-binding accord brokered by President Barack Obama in the final hours of the December climate change summit in the Danish capital.

On Monday, India sent a note that it "stands by the contents of the accord."

More than 100 countries had earlier replied to a query by Denmark whether they wanted to be "associated" with the accord.

The official messages to the UN climate change secretariat did little to ease the pessimism that a legal international agreement on global warming can be concluded this year.

AP