The world's two most powerful countries are involved in an escalating dispute over territory in the South China Sea.

China has nearly finishing developing artificial islands in an area the US-allied Philippines has also claimed, and it's feared that they will be used as military and naval bases to intimidate other countries and dominate the oil-rich region — which also happens to be one of the world's most important commercial waterways.

China says it has sovereignty over the Spratly Islands, and there's no hostile intent. Vietnam, Malaysia, Taiwan and Brunei also have claims in the South China Sea.

US Navy Admiral Harry Harris told the Senate China's militarisation in the region is of "great concern" and pressed for patrols close to "those islands that are not islands."

Republican Senators, including John McCain, told the Pentagon to take actions that challenge China's claim to the territory.

China's territorial disputes Show all 5 1 /5 China's territorial disputes China's territorial disputes South China Sea A satellite image of what is claimed to be an under-construction airstrip at Fiery Cross Reef in the Spratly Islands in the disputed South China Sea China's territorial disputes South China Sea Chinese dredging vessels are purportedly seen in the waters around Mischief Reef China's territorial disputes South China Sea A Chinese Guided Missile Frigate Hengshui docked at a port in Yalong Bay in Sanya, south China's Hainan Province. China's military compared its controversial island reclamation project in the South China Sea to ordinary construction going on in other parts of the country, such as the building of roads and apartments China's territorial disputes South China Sea The alleged on-going land reclamation of China at Subi reef is seen from Pagasa island (Thitu Island) in the Spratlys group of islands in the South China Sea, west of Palawan, Philippines China's territorial disputes South China Sea U.S. military forces aboard Amphibious Assault Vehicles (AAV) manuevre on South China Sea near the shore of San Antonio, Zambales during the annual "Balikatan" (shoulder-to-shoulder) war games with Filipino soldiers in northern Philippines. The U.S. Marine Corps is bringing together foreign commanders from amphibious forces deployed mostly in the Asia-Pacific for a conference aimed at taking initial steps to integrate their operations, with China excluded from the event, according to officials and planning documents

The Chinese Foreign Ministry said it was "extremely concerned" by the comments, and that China was against "any country challenging China's sovereignty and security in the name of protecting freedom of navigation".

"We demand that the relevant country speak and act cautiously, earnestly respect China's sovereignty and security interests, and not take any risky or provocative acts."

Citing recent satellite footage, US expert Bonnie Glaser has said China is continuing to reclaim land in the region despite saying it stopped more than a month ago.