US to China: Why Do You Need an Aircraft Carrier? China's first aircraft carrier set sail today for the first time.

Aug. 10, 2011  -- As China's first aircraft carrier takes to the open seas today for its inaugural sea trials, the U.S. government directed a pointed question at the Chinese military: Why would you need a warship like that?

"We would welcome any kind of explanation that China would like to give for needing this kind of equipment," U.S. State Department spokesperson Victoria Nuland told reporters today. "We have had concerns for some time and we've been quite open with them with regard to the lack of transparency from China regarding its power projection and its lack of access and denial of capabilities."

Nuland said the State Department is concerned that the Chinese military is not "transparent" enough about its build-up which, in addition to the aircraft carrier, also includes the development of a fifth-generation stealth jet fighter believed to be capable of rivaling America's best.

"We are prepared to be extremely transparent with regard to U.S. military positions and equipment, and we'd like to have a reciprocal relationship with China, and that's what our presidents have said we ought to aspire to," Nuland said. "Transparency in itself is a confidence builder between nations."

Chinese Defense Ministry spokesman Geng Yansheng told reporters in China last month the ship, that was built from the shell of an old Soviet carrier, is only "for the purposes of technological research, experiments and training."

But in June, another official with the Chinese Defense Ministry told a Hong Kong newspaper the vessel represented more than a training opportunity.

"All of the great nations in the world own aircraft carriers -- they are symbols of a great nation," Lt. Gen. Qi Jianguo, assistant chief of the general staff, told the Hong Kong Commercial Daily.

At the time, the U.S. Department of Defense told ABC News it was well aware of Chinese ambitions to build not one, but multiple aircraft carriers as part of an effort to modernize its military. The U.S. will "maintain the military capabilities necessary to protect our interests, defend our allies, and deter potential adversaries from acts of aggression and intimidation," a spokesperson said then.

As the 990-ft., 67,500-ton ship, which was known as the Varyag when it was in construction by the Soviet Union before its collapse, left its port at Dalian for the first time today, Taiwanese officials made the timely announcement that it had developed an "aircraft carrier killer" of a missile, according to the Associated Press.

Taiwan and China split in 1949 after a bloody civil war and China has publicly stated that it means to bring Taiwan back under its flag. Though the U.S. "does not support Taiwan's independence," it maintains an "unofficial" relationship with the territory and is opposed to "any attempt by either side to unilaterally alter the status quo in the Taiwan Strait," the State Department website says.

In addition to perceived security woes for Taiwan, the development of the carrier also comes as China has expanded its rhetoric regarding its claims in the South China Sea -- where as many as six Asian countries have claimed overlapping territorial waters -- while telling the U.S. to stay out of it.

The Associated Press contributed to this report.