WASHINGTON — The Pentagon announced on Tuesday that it mistakenly shipped non-nuclear components for an intercontinental ballistic missile to Taiwan from a U.S. Air Force base in Wyoming.

It said the items have been returned to the United States.

At a Pentagon news conference, Air Force Secretary Michael Wynne said the misshipped items were four nose cone assemblies for ICBMs. He also said they were delivered to Taiwan in March 2006 and had been sent instead of helicopter batteries that had been ordered by Taiwan.

"This could not be construed as being nuclear material. It is a component for the fuse in the nosecone for a nuclear system," Wynne said. "We are very concerned about it."

Wynne said the matter is under investigation. He said the Taiwanese authorities notified U.S. officials of the mistake.

The Chinese Embassy did not immediately respond to a request for comment. A Taiwan official said Tuesday that the island's diplomats in Washington typically do not comment on Defense Department matters.

Ryan Henry, the No. 2 policy official in the office of Defense Secretary Robert Gates, said President Bush was notified of the mistake and the actions to recover the items. Henry called the mistake "disconcerting" and intolerable. He said the Chinese government has been notified of the error.

Henry said an examination of the site in Taiwan where the components had been stored after delivery indicated that they had not been tampered with. He said the components were "quite dated," as part of a system designed in the 1960s.