Nothing projects U.S. global air and sea power more vividly than supercarriers. Bristling with fighter jets that can reach deep into even landlocked trouble zones, America’s virtually invincible carrier fleet has long enforced its dominance of the high seas.

China may soon put an end to that.

U.S. naval planners are scrambling to deal with what analysts say is a game—changing weapon being developed by China, an unprecedented carrier—killing missile called the Dong Feng 21D that could be launched from land with enough accuracy to penetrate the defences of even the most advanced moving aircraft carrier at a distance of more than 1,500 kilometers (900 miles).

Analysts say final testing of the missile could come as soon as the end of this year, though questions remain about how fast China will be able to perfect its accuracy to the level needed to threaten a moving carrier at sea.

The weapon, a version of which was displayed last year in a Chinese military parade, could revolutionize China’s role in the Pacific balance of power, seriously weakening Washington’s ability to intervene in any potential conflict over Taiwan or North Korea. It could also deny U.S. ships safe access to international waters near China’s 11,200—mile (18,000—kilometer) —long coastline.

While a nuclear bomb could theoretically sink a carrier, assuming its user was willing to raise the stakes to atomic levels, the conventionally—armed Dong Feng 21D’s uniqueness is in its ability to hit a powerfully defended moving target with pin—point precision.

The Chinese Defence Ministry did not immediately respond to the AP’s request for a comment.

Funded by annual double—digit increases in the defence budget for almost every year of the past two decades, the Chinese navy has become Asia’s largest and has expanded beyond its traditional mission of retaking Taiwan to push its sphere of influence deeper into the Pacific and protect vital maritime trade routes.

“The Navy has long had to fear carrier—killing capabilities,” said Patrick Cronin, senior director of the Asia—Pacific Security Programme at the nonpartisan, Washington—based Centre for a New American Security. “The emerging Chinese anti-ship missile capability, and in particular the DF 21D, represents the first post—Cold War capability that is both potentially capable of stopping our naval power projection and deliberately designed for that purpose.”

Setting the stage for a possible conflict, Beijing has grown increasingly vocal in its demands for the U.S. to stay away from the wide swaths of ocean, covering much of the Yellow, East and South China seas, where it claims exclusivity.

It strongly opposed plans to hold U.S.—South Korean war games in the Yellow Sea off the north-eastern Chinese coast, saying the participation of the USS George Washington super-carrier, with its 1,092—foot (333—meter) flight deck and 6,250 personnel, would be a provocation because it put Beijing within striking range of U.S. F—18 warplanes.

The carrier instead took part in manoeuvres held farther away in the Sea of Japan.

U.S. officials deny Chinese pressure kept it away, and say they will not be told by Beijing where they can operate.

“We reserve the right to exercise in international waters anywhere in the world,” Rear Adm. Daniel Cloyd, who headed the U.S. side of the exercises, said aboard the carrier during the manoeuvres, which ended last week.

But the new missile could undermine that policy.

“China can reach out and hit the U.S. well before the U.S. can get close enough to the mainland to hit back,” said Toshi Yoshihara, an associate professor at the U.S. Naval War College. He said U.S. ships have only twice been that vulnerable, against Japan in World War II and against Soviet bombers in the Cold War.

Carrier—killing missiles “could have an enduring psychological effect on U.S. policymakers,” he e—mailed to The AP. “It underscores more broadly that the U.S. Navy no longer rules the waves as it has since the end of World War II. The stark reality is that sea control cannot be taken for granted anymore.”

Mr. Yoshihara said the weapon is causing considerable consternation in Washington, though, with attention focused on land wars in Afghanistan and Iraq, its implications haven’t been widely discussed in public.

Analysts note that while much has been made of China’s efforts to ready a carrier fleet of its own, it would likely take decades to catch U.S. carrier crews’ level of expertise, training and experience.

But Beijing does not need to match the U.S. carrier for carrier. The Dong Feng 21D, smarter, and vastly cheaper, could successfully attack a U.S. carrier, or at least deter it from getting too close.

U.S. Defence Secretary Robert Gates warned of the threat in a speech last September at the Air Force Association Convention.

“When considering the military—modernization programmes of countries like China, we should be concerned less with their potential ability to challenge the U.S. symmetrically, fighter to fighter or ship to ship, and more with their ability to disrupt our freedom of movement and narrow our strategic options,” he said.

Mr. Gates said China’s investments in cyber and anti—satellite warfare, anti—air and anti—ship weaponry, along with ballistic missiles, “could threaten America’s primary way to project power” through its forward air bases and carrier strike groups.

The Pentagon has been worried for years about China getting an anti—ship ballistic missile. The Pentagon considers such a missile an “anti—access,” weapon, meaning that it could deny others access to certain areas.

The Air Force’s top surveillance and intelligence officer, Lt. Gen. David Deptula, told reporters this week that China’s effort to increase anti—access capability is part of a worrisome trend.

He did not single out the DF 21D, but said- “While we might not fight the Chinese, we may end up in situations where we’ll certainly be opposing the equipment that they build and sell around the world.”

Questions remain over when, and if , China will perfect the technology; hitting a moving carrier is no mean feat, requiring state—of—the—art guidance systems, and some experts believe it will take China a decade or so to field a reliable threat. Others, however, say final tests of the missile could come in the next year or two.

Former Navy commander James Kraska, a professor of international law and sea power at the U.S. Naval War College, recently wrote a controversial article in the magazine Orbis outlining a hypothetical scenario set just five years from now in which a Deng Feng 21D missile with a penetrator warhead sinks the USS George Washington.

That would usher in a “new epoch of international order in which Beijing emerges to displace the United States.”

While China’s Defence Ministry never comments on new weapons before they become operational, the DF 21D, which would travel at 10 times the speed of sound and carry conventional payloads, has been much discussed by military buffs online.

A pseudonymous article posted on Xinhuanet, website of China’s official news agency, imagines the U.S. dispatching the George Washington to aid Taiwan against a Chinese attack.

The Chinese would respond with three salvos of DF 21D, the first of which would pierce the hull, start fires and shut down flight operations, the article says. The second would knock out its engines and be accompanied by air attacks. The third wave, the article says, would “send the George Washington to the bottom of the ocean.”

Comments on the article were mostly positive.