Washington: US Defence Secretary Ash Carter has warned China against aggression in the South China Sea, saying the nation is bucking positive regional cooperation in Asia in pursuit of its own ambitions. Carter made the remarks on Friday at the International Institute for Strategic Studies (IISS) Shangri-La Dialogue in Singapore, an annual conference addressing security in the Asia-Pacific region, CNN reported. "China's actions in the South China Sea are isolating it at a time when the entire region is coming together and networking," Carter said, adding "Unfortunately, if these actions continue, China could end up erecting a Great Wall of Self-Isolation." Beijing's claim to almost the entire South China Sea is a major source of tension in the region, as the Philippines, Brunei, Malaysia and Vietnam have also claimed territory in the area, which is rich in natural resources and a key zone for navigation routes. The US has protested China's shows of force in the region. Asked by a Chinese professor in a question-and-answer session why the US was focusing on China, Carter said it should not be interpreted as a dispute between the two nations. "What we stand for is the principle of the rule of law and abiding by international law," Carter said. "It's not a focus on China. It's a focus on principle." "It's China's actions that are causing that attention," Carter added. Carter's speech follows a keynote speech also on Friday from Thai Prime Minister Prayut Chan-O-Cha in which he also addressed the South China Sea, calling on rival claimants to "preserve peace and stability" in the region. The Thai premier listed tensions in the South China Sea and East China Sea as the first of seven security challenges that should be addressed "in order to find a new equilibrium."