WASHINGTON: China's activities in the disputed South China Sea are "destabilising" and may pose a threat to commercial trade routes in the region, a top US military general has said, asserting that such developments could erode America's "competitive advantage" in Asia."In the South China Sea, Chinese activity is destabilising and could pose a threat to commercial trade routes," General Joseph Dunford, Chairman of the Joint Chiefs of Staff, said before the Center for Strategic and International Studies, a top American think-tank."While our exercise of freedom of navigation provides some assurance to our allies and partners, it hasn't stopped the Chinese from developing military capabilities in the South China Sea, to include on territories where there is a contested claim of sovereignty," Dunford said yesterday.Noting that the US policy emphasises on opportunities to cooperate with regard to China, Dunford said the Pentagon was closely tracking China's rapid military modernisation, its expanded presence in Asia and increased military presence outside of Asia."While Chinese military investments , capability development and intentions are opaque, it's clear they're investing in a manner that balances requirements for large conventional forces, a growing navy, an increasingly sophisticated air force and advancements in nuclear, space and cyberspace," Dunford said."These developments, over time could erode our competitive advantage in Asia and they certainly will challenge our ability to assure access in a fight," he said.Dunford said the US is now confronted with simultaneous challenges from Russia, China, Iran , North Korea and violent extremism."The threat from the Islamic violent extremism is certainly the most pressing challenge we face right now," he said,adding that the Russian military presents the greatest array of threats to US interest."Despite declining population, shrinking economy , Russia has made a significant investment in military capabilities," he said.Dunford said the dreaded ISIS is clearly a transregional threat and the US was looking for an opportunity to address the wider challenge."While the fight against ISIL dominates the headlines, we also continue to face an extremist challenge in the homeland and our interest in South Asia ," he said."From my perspective, the constant pressure we put on al Qaeda in that region over the past 14 years has prevented another 9/11, but the threat has not been eliminated - and of course, I'm talking about largely the Afghanistan-Pakistan region," Dunford said.Pitching for an effective counterterrorism partner and platform in Afghanistan," Dunford said while the focus had been on al Qaeda, the recent rise of the IS in the Khorasan has further complicated the situation in Afghanistan and Pakistan.