Washington ? The U.S. military’s mistaken delivery to Taiwan of electrical fuses for an intercontinental ballistic missile raised concerns Tuesday over U.S.-China relations and triggered a broad investigation into the security of Pentagon weapons.

While the shipment did not include nuclear materials, the error is particularly sensitive because China vehemently opposes U.S. arms sales to Taiwan. Four of the cone-shaped fuses were shipped to Taiwanese officials in fall 2006 instead of the helicopter batteries they had ordered.

Despite quarterly checks of the inventory, defense officials said they never knew the fuses were gone. Only after months of discussions with Taiwan over the missing batteries did the Pentagon finally realize – late last week – the gravity of what had happened.

Once the error was discovered, the military quickly recovered the four fuses. How it happened, and whether the incident constitutes a violation of any treaty or agreement governing international sales of missile technology, were lingering questions.

At a hastily called news conference Tuesday, Ryan Henry, the No. 2 policy official in Defense Secretary Robert Gates’ office, said President Bush as well as Chinese leaders were informed of the mistake – an error Henry called intolerable.

“I cannot emphasize forcefully enough how strong the secretary feels about this matter and how disconcerting it is to him,” Henry told reporters.

In a comment directed at the Chinese concerns, Henry said the error does not suggest that U.S. policies on arms sales to Taiwan have changed.

Taiwan, which split from China amid civil war in 1949, is the most sensitive issue in U.S.-China relations.