In recent years, Chinese and U.S. diplomats have brushed off any suggestion that the budding Asian superpower and the reigning global hegemon may enter into conflict, invariably citing the two countries' intertwined economies. But 2010 saw a dramatic hardening of potential battle lines. Beijing has been steadily building up its naval power, particularly its submarine fleet, in a way that some hawkish U.S. analysts believe is a direct challenge to American supremacy in the Pacific. Chinese outrage over Washington's sale of military equipment to Taiwan early this year a routine gesture that Beijing has ignored in the past and U.S. frustration over China's tacit support of North Korea overshadowed a high-profile summit of defense ministers in Singapore in June. Tensions spiked in the summer, as U.S. naval exercises with South Korea near the Yellow Sea were met by subsequent Chinese drills. Beijing also made a similar symbolic show of force in the South China Sea, a body of water which the Chinese claim exclusively, likening it to Tibet. But other nations such as Vietnam also claim suzerainty over parts of the South China Sea. In the face of an increasingly assertive China, a host of countries from Japan and Australia to Indonesia and India have edged closer to Washington this year. The tried-and-tested Pax Americana is still preferable to the deep uncertainties surrounding China's rise.