BEIJING — China’s official military budget will rise by just 7.5 percent in 2010, a government spokesman said Thursday, a rate that is about half the official increase in recent years and the first to fall below 10 percent since 1989.

The announcement by Li Zhaoxing, a spokesman for the National People’s Congress, China’s legislature, gave no explanation for the slowdown. Some analysts speculated, however, that China’s huge economic stimulus program and other efforts to address unemployment and welfare had eaten into monies that in a normal year would go toward defense.

It is also possible that China reduced the growth of its publicly acknowledged defense spending to help allay international concerns about its rising power.

While China’s government has disclosed more information about military spending in recent years, much of its spending remains secret, and, in the past, military experts in the United States and elsewhere have said Beijing’s real military spending is at least double the announced figure. A 2009 Pentagon report estimated China’s total military spending to be between $105 billion and $150 billion. While growing rapidly, China’s military spending is still dwarfed by that of the United States, which has about $719 billion in outlays this year for national defense.