WASHINGTON, June 27 (Reuters) - The US Senate unanimously approved a resolution on Monday that deplored China's use of force against Vietnamese and Philippine ships in the South China Sea. China has shown increasing assertiveness in its claim to the entire South China Sea, believed to be rich in oil and gas. In its nonbinding resolution, the US Senate said it deplored the use of force by Chinese vessels and urged all parties to refrain from using force to assert territorial claims. Senator Jim Webb, chair of an east Asian and Pacific affairs subcommittee of the Senate Foreign Relations Committee, said the resolution was "a significant development toward fostering a multilateral approach to resolve these territorial disputes." "A growing number of nations around the South China Sea are now voicing serious concerns about China's pattern of intimidation," said Webb, who introduced the resolution. Chinese vessels have harassed Vietnamese oil exploration ships and the Philippines has also complained that one of its ships has been rammed, according to the Senate resolution. On Sunday, China and Vietnam pledged to resolve their maritime dispute through peaceful negotiations, a sign of possibly easing tension. The dispute was one of several subjects discussed in the first set of talks in Hawaii between the United States and China over the weekend.