The Obama administration has added to the growing trade battles with China even before Donald Trump takes office, launching a World Trade Organisation challenge to Chinese restrictions on grain imports.

The latest US case is focused on China’s administration of import quotas for corn, rice and wheat, which Washington claims unfairly limit its exports to China. It is the 15th WTO action brought against Beijing by the Obama administration.

The case highlights how trade and other tensions between the US and China are escalating even as Mr Trump and his administration prepare to take over, having promised to take a hard line with Beijing on trade and other issues. It also points to broader fears about how the Republican president-elect will manage the world’s most important economic relationship.