US denies China's allegations of naval intrusion in the South China Sea

China accuses US of violating sovereign waters in South China Sea; USS Gabrielle Giffords allegedly illegally intruded near Second Thomas Shoal; Chinese naval force monitors American warship's movements; Philippines seeks American assistance in territorial conflicts; China accuses US of meddling in the region, escalating tensions; USS Gabrielle Giffords becomes focal point of dispute; China insists on its right over the South China Sea; concerns over potential for further military confrontations