The Pentagon is contemplating sending ships and military aircraft to disputed South China Sea to increase presence in the region.
US Defense Secretary Ash Carter asked his staff to come up with options to protect US interests in the region, including the alternative of sending US military ships and aircraft within 12 nautical miles of artificial islands that China has been building up on reefs near the disputed Spratly Islands.
China has been building islands on reefs in the area to increase its influence and control in the strategically important region.
"We are considering how to demonstrate freedom of navigation in an area that is critical to world trade," the official said.
Increased US military presence challenges China’s ambitions to expand its influence.
The Philippines and Japan, two US allies with stakes in the disputed region, held their first joint naval exercises in the South China Sea on Tuesday.
The Philippines, Brunei, Malaysia, Taiwan and Vietnam, as well as China lay claim to parts of the Spratly Islands.
A series of satellite images show that China has intensified the construction of artificial islands in the area, sometimes doubling or tripling the size of existing features.
US estimates China created about 2,000 acres of artificial land since the start of 2014.
South China Sea is a vital shipping route and plays an important role in international trade as every year around $5 trillion worth of goods transferred through the region.