SAN DIEGO, Calif, March 21 (Reuter) - Three Chinese warships sailed into port on Friday in the first ever visit of naval vessels from the People's Republic of China to the American mainland.

Vice Admiral Brent Bennitt, commander of the U.S. Pacific Fleet's Naval Air Force, welcomed the 600 officers and crew of the two destroyers and an oil supply vessel and called their visit "a major milestone between China and the United States."

Later, in brief remarks to reporters, he said, "It's important for us to expand this cooperation. This is a small step."

Before mooring off San Diego, the three ships had briefly visted Hawaii.

As the first ship, the destroyer Harbin, docked at 9:55 a.m. PST (12.55 a.m. EST) a Navy brass band played "Sing, Sing, Sing," followed by Aaron Copland's "Fanfare for the Common Man."

The Harbin was followed into the docks by the destroyer Zhuhai and the oiler Nancang at 11 a.m PST (2 p.m. EST) and two Chinese admirals, Vice Admiral Wang Yongguo, commander of China's South Sea Fleet, and Rear Admiral Li Xiukang, strode ashore on mainland U.S. soil for the first time since the Communists took over China in 1949.

Except for a sailboat passing earlier with the banners "Human Rights for China" and "Free Tibet," there was little protest on Friday.

"The futures of our two nations are more closely tied than ever before," Bennitt told a crowd of dignitaries from the local Chinese-American community. Wang also told the crowd, through a translater, that his country was committed to improving relations with the United States.

"This is very important to us," said Robert Mar, 65, who was among some 400 Chinese-Americans watching the arrival. He said he was there to meet two of his wife's relatives serving aboard one of the ships. "I'll know them by their faces," he said.

The Harbin, one of China's more modern warships, was built from equipment supplied by several countries, including the United States, and commissioned in 1994.

While the ships are moored for the next five days their crews will mingle with American sailors and visit nearby Disneyland and the San Diego Zoo. The public will be able to tour the ships on Saturday and Sunday.

The visit was negotiated during a December visit to Washington by Chinese Defence Minister Chi Haotian. Despite differences over trade, human rights, Taiwan and arms proliferation, the United States and China have moved in recent months to improve relations. President Bill Clinton has stressed the importance of engaging China rather than isolating it.