By ERIK ECKHOLM, THE NEW YORK TIMES

BEIJING -- China's chief of arms control issued a new warning yesterday that U.S. plans for a national missile defense system, even if intended to stop attacks from countries like North Korea and Iraq, would set off a global arms race and cause more countries to develop nuclear weapons.

The existing Anti-ballistic Missile Treaty, which the United States proposes altering to allow limited defenses, has long been a cornerstone of nuclear stability, Sha Zukang, director of arms control and disarmament in China's foreign ministry, said yesterday in an article in the official newspaper China Daily.

"Amending it in search of national missile defense will tip the global balance, trigger a new arms race and jeopardize world and regional stability," Sha wrote.

Russia, the main nuclear rival of the United States, has also been vociferous in opposing missile defenses.

China has objected to proposed theater missile defenses, local systems intended to protect American allies in Asia from missile attacks.

China worries that such high-technology defenses would be offered to Taiwan, cementing military ties between Taiwan and the United States.

Though the debate is already heated, theater defenses that could stop a blitz of short-range missiles are still in the unproved research stage.

But in yesterday's article and recent speeches, Chinese officials have also vehemently challenged the progressing American plans for a national defense system, perhaps designed to stop a handful of incoming missiles.

A prime reason for Chinese concern, weapons experts say, is that even a limited system would undercut China's own nuclear strategy, forcing it to spend far more than it wants to build extra rockets and bombs.

Unlike the United States and Russia, China has deployed small numbers of weapons intended simply to give adversaries second thoughts about attacking it.