WASHINGTON — China’s high-flying economy is starting to lose altitude. The big question is whether the world’s economic superstar will shrink gradually — or so fast that it harms a fragile global economy.

China’s comedown is being engineered by its policymakers. They want to slow expansion just enough to cool inflation without sapping job growth.

It’s a delicate task.

“Nobody can say with any confidence” if they’ll succeed, says Barry Eichengreen, an economics professor at the University of California, Berkeley.

China’s explosive growth remains the envy of developed nations like the United States. It grew faster than any other major economy in the April to June quarter, according to The Associated Press’ latest quarterly Global Economy Tracker. Only Argentina’s much smaller economy matched China’s 9.5 percent annual growth rate.

By contrast, the U.S. economy grew at a 1.3 percent rate in the April-June quarter, before expanding 2.5 percent in the July-September period.

The AP’s Global Economy Tracker monitors economic and financial data in 30 countries representing more than 80 percent of global output.

Economists worry that China’s economy could suffer what they call a “hard landing.” They fear that a sudden plunge in China’s growth would harm the economies of the United States, Europe and small countries that need China to buy their coal, copper and other raw materials.

That threat comes as the United States is still struggling to recover from the Great Recession of 2007 to 2009. And an agreement last week to ease Europe’s debt crisis might not prevent the continent from sliding back into a recession that would ripple through the United States and other countries.

When surveyed this year by the Society of Actuaries, corporate risk managers in the United States, Canada and elsewhere said a slowdown in China posed the greatest threat to their business.

A hard landing wouldn’t just squeeze U.S. and European exporters. It could also destabilize Chinese society. And it could escalate global trade tensions.

Hampered by high inflation and declining exports, China’s growth is expected to decelerate from 10.3 percent last year to 9.5 percent in 2011 and 9 percent in 2012, according to the International Monetary Fund. The IMF expects the global economy to grow 4 percent this year.

Developing countries emerged almost unscathed from the Great Recession. They’re now growing much faster than rich countries. According to the AP’s global tracker:

n The three fastest in the April to June quarter were China (a 9.5 percent annual growth rate), Argentina (9.5 percent) and Indonesia (6.5 percent).

n The laggards are from the industrialized world — Japan (down 1.1 percent), Norway (up 0.3 percent) and Britain (up 0.6 percent).

n Growth is slowing worldwide. It weakened from a year earlier in 19 of 26 countries that reported April-June data.

China’s gaudy growth doesn’t mean much to Xie Jun, who runs a factory in the southern Chinese boomtown of Dongguan. He’s enduring a tough year.

His company makes and exports headphones, cell phones and computer accessories.

It’s paying 30 percent to 50 percent more this year for chemicals, fuel and other raw materials. Labor costs have nearly doubled.

Xie’s customers are reducing orders, forcing him to lay off more than 10 percent of his staff at Dongguan Jincai Real Co.

“I just feel hopeless,” Xie, 45, says. “It’s hard to say if it will get any better next year.”