BEIJINGâ€”China's Defense Ministry said its first aircraft carrier would be used for "research, experiments and training" and would not affect its defensive naval strategy, in an apparent attempt to ease regional concerns that the vessel could be used to enforce Chinese territorial claims. Senior Col. Geng Yansheng, a Defense Ministry spokesman, also confirmed for the first time that Chinese pilots were training to operate from the carrier, which is based on an empty hull bought from Ukraine, and which is due to start sea trials this summer. But he said it would take a long time to become fully operational. "Building an aircraft carrier is extremely complex and at present we are using a scrapped aircraft carrier platform to carry out refurbishment for the purposes of technological research, experiments and training," Col. Geng said, according to a Chinese transcript of a monthly Defense Ministry news conference published on its web site. Asked about media reports that the vessel would be launched on Aug. 1, China's Army Day, he said: "There is not a question of when this ship is launched, because it has been in the water all along. As for the precise timetable for the ship beginning sea trials, it will be decided according to the schedule of the refurbishment project." He also dismissed a question suggesting that China's sudden relative openness about the carrier was linked to recent tensions in the South China Sea, where China has conflicting territorial claims with Vietnam, the Philippines, Taiwan, Malaysia and Brunei, and has warned the U.S. to stop reconnaissance operations. "To construct and use a carrier requires the integration of various types of weaponry, and requires synergy in every area," Col. Geng said. "This will be a long and slow process." A Chinese company purchased the empty hull of a carrier called the Varyag from Ukraine in 1998, on the understanding that it would be used as a floating casino, but it was later towed to the northeastern port of Dalian, where it has been undergoing refurbishment ever since. China's plans to reactivate the carrier for its navy have been known for years. The vessel is easily visible from parts of Dalian and photographs and video footage of the refurbishing have been published online. But China did not officially confirm its plans until earlier this month, when Gen. Cheng Bingde, the Chief of General Staff of the People's Liberation Army, spoke about it at a news conference after meeting Mike Mullen, the U.S. chairman of the Joint Chiefs of Staff, in Beijing. Gen. Chen did not, however, say how China planned to use the carrier. The vessel is significant as it will give China, for the first time, the theoretical ability to project air power far from its shores, as well as providing crucial experience for developing its own, larger indigenous carriers, the first of which some defense experts say is already under construction. It would take China several decades to match the U.S.'s current carrier fleet of 11, but Beijing only needs a few to enhance its ability to deny U.S. forces access to waters around China in the event of a regional conflict, or to protect its shipping lanes and other perceived national interests overseas. To be effective, at least two or three carriers are required, so that at least one can remain active while another undergoes repairs, and each active one requires its own carrier group including several other vessels, according to Chinese and foreign defense experts. For the moment, therefore, they say the Varyagâ€”which has yet to be renamedâ€”will likely be used mainly to test equipment and train personnel, especially pilots who must learn to take off from and land on the carrier while it is moving. Some also say that it could be used for limited patrols around China's territorial waters, as well as visits to foreign countries to try to enhance military relations and help them grow accustomed to China's newfound naval strength. Col. Geng said that a carrier could be used for offensive or defensive purposes as well as for disaster relief, and that China was pursuing its carrier program "in order to increase its ability to protect national security and world peace." "China's firm adherence to a defensive national defense policy will not change because of the development of advanced weapons," he said. "China's naval strategy of inshore defense also has not changed."