The US sought to downplay the significance of images of a Chinese J-20 stealth fighter prototype first published online on Wednesday, Reuters reported. US Vice Admiral David Dorsett, director of naval intelligence, said the images left a lot of questions unanswered. He noted that even if a prototype has been developed, it would be years before China could integrate it into a combat environment. Nevertheless, the disclosure of the images is likely to heighten US concerns about China’s military buildup, with Defense Secretary Robert Gates due to travel to Beijing on Sunday. It has been suggested that Beijing might deploy its first aircraft carrier in 2011 as well as a new anti-ship ballistic missile. Separately, the head of the Institute for Defense Economics at China’s National Defense University on Wednesday called for the country to increase its military spending to 2.8% of GDP, up from the current 1.4%. The appeal is seen as part of lobbying efforts for funds under China’s 12th Five-Year Plan, which is due for release this year.