The potentially volatile incident came to light as Adm. Gary Roughead, commander of the U.S. Pacific Fleet, began a visit to China to coordinate a Nov. 19 joint search-and-rescue exercise aimed at strengthening ties between the two navies.
Roughead said Chinese military officials he met told him the submarine was in international waters, indicating that it was not encroaching on any territorial rights.
The submarine "was operating in a manner that did not hazard any vessel or cause any problems for any vessel," Roughead said in an interview.
"I do believe ... that the openness and transparency and the ability to communicate when our forces are operating in proximity with one another is very important," said Roughead. "That's why we are doing this series of exercises."
China has denied a report by The Washington Times that the submarine had followed a U.S. carrier group in the Pacific Ocean and surfaced within torpedo firing range.
The Times report said the Chinese submarine "stalked" the Kitty Hawk and surfaced within 5 miles of the carrier group, which had been operating near the southern Japanese island of Okinawa at the time of the incident.
Adm. William Fallon, the commander of U.S. Pacific Command, said this week that the carrier group was not engaged in anti-submarine exercises. But if it had, "and if this Chinese sub came in the middle of this, then it could have escalated into something that could have been very unforeseen," said Fallon, who was in Kuala Lumpur, Malaysia, for a defense meeting.
Chinese Foreign Ministry spokeswoman Jiang Yu said Thursday that the Times report was "not in line with fact" but did not elaborate.
Visits between the Chinese and American militaries dropped off after the collision of a U.S. spy plane and a Chinese fighter jet off China's coast in 2001.
Relations have been improving recently as U.S. leaders cautiously seek to increase exchanges and better understand China's rapidly modernizing People's Liberation Army, the world's largest.
In September, two Chinese navy ships stopped in Pearl Harbor in Hawaii — the first at a U.S. state in six years. After Pearl Harbor, the ships went to San Diego in southern California for the first part of the search-and-rescue exercise that will end Sunday off the island province of Hainan.
Roughead said about 400 Navy personnel from the USS Juneau will participate in the exercise, which will last several hours.