The commander of the U.S. Pacific Fleet on Tuesday accused China of building a "great wall of sand" through land reclamation in the South China Sea, the Associated Press reported.

The effort is causing serious concerns about Beijing's territorial intentions, Adm. Harry Harris told a naval conference in Australia.

The People's Republic claims virtually all of the South China Sea, a stance that has sparked territorial disputes with the Philippines and other countries that are increasingly concerned by the land-reclamation projects, the news service noted.

"China is building artificial land by pumping sand on to live coral reefs -- some of them submerged -- and paving over them with concrete," Harris explained. "China has now created over 4 square kilometers of artificial landmass," he added.

The U.S. admiral spoke on Tuesday night at the Australian Strategic Policy Institute, a Canberra think tank charged with developing ideas on the Oceanic country's defense and strategic policy options; China is Australia's largest trading partner.

Harris' comments mark "his most direct public criticism" of the Chinese project, which centers on the contested Spratly Islands archipelago, a group of more than 750 reefs, islets, atolls, cays and islands also claimed by Brunei, Malaysia, the Philippines, Taiwan and Vietnam, the Wall Street Journal detailed.

"When one looks at China's pattern of provocative actions towards smaller claimant states ... it's no surprise that the scope and pace of building man-made islands raises serious questions about Chinese intentions," Harris argued. "How China proceeds will be a key indicator of whether the region is heading towards confrontation or cooperation," the admiral added.

The United States has said that a peaceful resolution of the dispute in a region vital for world trade is in its national interest, and, according to the Washington Post, Harris urged all parties to conform to the 2002 China-ASEAN Declaration of Conduct.

In the document, the claimants committed, among other things, to "self-restraint in the conduct of activities that would complicate or escalate disputes and affect peace and stability.

Beijing, nevertheless, has insisted that its territorial claims have a historical basis and objects to what it considers U.S. meddling, the Washington newspaper noted.