The three-day visit by Locke and Chu precedes a Sino-US strategic dialogue in Washington later this month, with the two nations still at loggerheads over reductions in carbon emissions.

China insists on keeping the principle of 'common but differentiated responsibilities' under a UN framework, with developed nations taking the lead on emissions reductions.

But Locke Wednesday reiterated the US position that large developing nations such as China and India must also play an important part in curbing global carbon emissions.

'It's been said that it's unjust to ask China and other developing nations to drastically reduce their carbon emissions, when countries like the US have spent 150 years using coal, oil and other dirty fuels to grow their economies,' Locke said.

'That's an understandable point, but one of no concern to Mother Nature,' he said.

'She doesn't discriminate between carbon that comes from the US or China, Europe or India. And she will ignore attempts to explain the sins of the future by pointing out sins others made in the past,' he said.

The US and the European Union filed complaints with the World Trade Organisation in June over China's restrictions of exports and hoarding of nine raw materials used by the steel, aluminium and chemical industries.

Other recent trade disputes cover issues including US limits on Chinese poultry and steel imports.