Berlin (AFP) - China will "steadfastly" implement the Paris climate pact, Premier Li Keqiang said Thursday, urging others to do likewise as US President Donald Trump was due to announce whether he will keep Washington in the deal.

"China will continue to implement promises made in the Paris Agreement, to move towards the 2030 goal step by step steadfastly," Li said in a Berlin joint press conference with German Chancellor Angela Merkel.

"But of course, we also hope to do this in cooperation with others," added Li.

China has been investing billions in clean energy infrastructure, as its leaders seek to clear up the notorious choking pollution enveloping its biggest cities, including Beijing.

Li stressed that it was in China's own interest to stick to the climate deal.

"Once China's development reaches a certain level, it has to move to a sustainable model, that means we have to push green development," he said.

In Berlin, Li and Merkel oversaw the signing of a slew of deals including electric car projects between Germany's biggest automobile groups, Volkswagen and Daimler, with Chinese companies.

China and the US are together responsible for some 40 percent of the world's emissions and experts have warned that it is vital for both to remain in the Paris agreement if it is to have any chance of succeeding.