MANILA (Reuters) - China should act responsibly in disputed territories in the South China Sea to avoid political and security issues, the skipper of the U.S. Navy's 7th Fleet flagship said on Wednesday.

Southeast Asian states, including the Philippines, have become worried by China's increasingly aggressive stance on the complex set of disputes in the South China Sea.

Last week, Chinese naval forces carried out drills in the disputed southern waters amid tension with Washington over security in the Korean peninsula and South China Sea.

Last year, there was a collision between sonar equipment being towed by a U.S. Navy warship and a Chinese submarine near Philippine waters.

Lupton said the United States viewed the South China Sea as part of international waters, where global trade passes through freely, and everyone was entitled to operate in that area.

"We conduct operations here and China can operate in waters adjacent to China," Lupton told reporters after USS Blue Ridge docked at Manila's south harbor for a four-day visit. "Our president has said he doesn't view China as a threat."

The United States has urged the several states claiming dozens of atolls and islets, some believed to be holding valuable oil and mineral assets, to settle the disputes peacefully.

China's growing might military might and rising defense spending have set alarm bells ringing around the region, particularly in Japan and Taiwan. It has repeatedly said its claims on the southern waters and island are indisputable.

It has said it will respect the freedom of navigation in the South China Sea as long as ships and aircraft transiting through "comply with international law".

U.S. Navy ships pay routine port calls in Manila under a Cold War-era mutual defense treaty. The U.S. Navy's 7th Fleet's home port used to be in Subic Bay, north of Manila, until November 1992 when the Philippines did not renew its U.S. bases deal.

(Editing by John Mair)