GETTY Obama and Xi could be set for a showdown

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The US President is discussing the possibility of sending artillery units to the hotly contested region – where China is said to be building military bases on artificial islands. A senior US defence chief has said the plan to install defensive gun positions in the region could soon go ahead.

GETTY China has already deployed two scary new missile batteries

The source said: "A Howitzer can go where it has to go. It is a way of changing an offensive weapon and using it in dual capacity. "This opens the door to opportunities and options we have not had before with mobile defensive platforms and offensive capabilities."

AFP/GETTY Protesters wave flags saying the South China Sea does not belong to China

Officials suggest similar weapons could be used in Eastern Europe to challenge Vladimir Putin. The potential deployment raises the worrying prospect of clashes between U.S. forces and Chinese jets, which are readily dispatched to islands controlled by Beijing. The Chinese government has already accused Washington of stirring tensions in the volatile region – and an increased U.S. presence could set the two superpowers on a collision course.