China and the United States carried out "very successful" joint naval exercises this month, agreeing on and actually employing communication protocols for the first time, the U.S. Pacific Fleet commander said Monday.

"They were a very positive step forward to the navy-to-navy relationship," Adm. Gary Roughead said at a Foreign Press Center news conference, referring to the communication exercise held early this month in Hawaii and a search-and-rescue drill last week off San Diego, California.

Roughead acknowledged the two nations will next hold the drills in China, saying, "We look forward to the second search-and-rescue exercises to be conducted in China."

U.S. defense officials said the next exercises will be conducted sometime this fall.

The drills were the first of their kind held by the two nations. They were carried out as part of the ongoing bilateral confidence-building efforts over past few years to restore military dialogue and ties that had severed after a U.S. spy plane and a Chinese fighter collided over the South China Sea in 2001.

Roughead said the exercises were also "unique" because the two sides used "some agreed communication protocols" for the first time.

"I was pleased that we were able to develop the communication protocols," he said, noting the two sides were also able to actually employ them in basic naval maneuvering and search-and-rescue operations.

The drills involved two Chinese naval ships -- the destroyer Qingdao and the oiler Hongzehu. They made port calls in Hawaii and San Diego to mark the first visit to the United States, except for Guam, by a Chinese warship since 2000.

Speaking earlier Monday at seminar sponsored by the Henry L. Stimson Center, a Washington-based think tank, Roughead said the United States is closely monitoring a reported Chinese plan to possess an aircraft carrier.

But he played down such a Chinese move in terms of military capability and power balance, stressing that owning an aircraft carrier and actually operating it is a "very difficult thing" as carrier operations are "complex."