The phone call came amid warnings that the conference scheduled for Copenhagen in December will fall short of ambitious hopes for agreeing a global climate change treaty to replace the Kyoto accord.

"The President spoke with President Hu on Tuesday night, October 20," the White House said in a statement, detailing the call between the leaders of the world's two largest emitters of greenhouse gases.

"They exchanged views on bilateral issues and climate change. Both leaders acknowledged each is taking significant actions to confront climate change and reduce emissions."

"President Obama noted the importance of working toward a successful outcome at the December Copenhagen Conference and the importance of leadership from the United States and China in that regard.

"To that end, the two Presidents committed to having their teams redouble efforts to work with each other and other countries to achieve success at Copenhagen."

Earlier, China's official Xinhua news agency said that Hu specifically spoke to Obama about dimmed hopes of substantial progress in Copenhagen.

"Although negotiations are currently fraught with all kinds of problems that need to be resolved, as long as all sides extend their hands and make efforts there is hope the Copenhagen meeting can make positive progress."

The two nations are the world's largest emitters of the greenhouse gases blamed for global warming and are seen as key to the success of global negotiations.

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