"I think you're generating more concern than perhaps is warranted," he told reporters.

But submarines of the type involved in the incident carry weapons capable of striking a carrier from a distance of more than 25 miles (40 km), an expert on the Chinese military said.

"Any time a potentially hostile submare operates in such proximity to critical naval assets like an aircraft carrier should be of concern to American military leaders," said Richard Fisher.

The Washington Times, which first reported the encounter, said the navy was reviewing its anti-submarine defenses and that China analysts at the Pentagon were surprised that a Chinese submarine was operating so far from the mainland.

Whitman said a US naval strike group led by the aircraft carrier USS Kitty Hawk was conducting routine training operations in the East China sea near Okinawa in October when the incident occurred.

"During these operations a Chinese Navy Song-class submarine was sighted near the strike group by US Navy aircraft," he said.

"My understanding is that this was several miles away," he said.

The Kitty Hawk was not actively engaged in anti-submarine warfare operations during the exercise, Whitman said, explaining why it did not detect the Chinese submarine sooner.

The Pentagon spokesman said he was not aware that any complaints had been lodged with the Chinese.

News of the incident came as commander of the US Pacific Fleed, Admiral Gary Roughead, was in Beijing for talks with Chinese military leaders ahead of a joint search and rescue exercise in the South China Sea.

"I really would like to know what the intent is in some of the developments that I see in the PLA navy," Roughead told reporters Monday.

He said these included the expansion of China's submarine fleet and procurement of ships.

"I look foward to having discussions about what the vision is and perhaps what some of the operating doctrine might be," Roughead said.

Fisher said incidents at sea between the two navies are likely to increase as China's ocean-going naval operations expand in the years ahead.

"It is my opinion the Chinese are going to be posturing against US military forces in Asia increasingly in the coming years," he told AFP.

"They are building a blue water navy. They have made clear in the past, a bit more subtly but consistently, that they are not at all accepting of the American military presence in what they see as their sphere of influence," he said.

He said China appears to be building a base on the tip of Hainan Island from which to deploy ballistic missile submarines and possibly future aircraft carriers across the South China Sea between China and Philippines.

"As a consequence I expect there may be many opportunities for naval incidents as the Chinese take exception to the presence of American navy ships transiting between northeast Asia and the Persian Gulf," he said.

Hainan Island was where a US Navy EP-3 surveillance plane collided with a Chinese fighter on April 1, 2001 in the last major US-Chinese military confrontation.

The latest incident occurred near Okinawa where the bulk of US forces in Japan are based.

"In the event of a general, out-of-the-blue Chinese attack against Taiwan, in my opinion they will also attack all American forces in Japan," Fisher said.

"Making sure their submarine commanders are familiar with operating around Okinawa or close to Japan is a competency the Chinese want to develop," he said.

Related Links
Pentagon
Learn about the Superpowers of the 21st Century at SpaceWar.com
China News From SinoDaily.com
Naval Warfare in the 21st Century