The US military was supposed to ship helicopter batteries to Taiwan, but instead sent fuses used as part of the trigger mechanism on Minuteman missiles, the Pentagon said on Tuesday.

Taiwan returned the parts to the US last week.

No nuclear material was shipped to Taiwan, Pentagon officials said.

Taiwan's Defence Minister Tsai Ming-hsien was asked in parliament by Nationalist Party legislator Lin Yu-fang whether the parts had been inspected by the Chung-Shan Institute of Science and Technology, a weapon's development body in Taiwan.

'As far as I know, no,' Mr Tsai said.

Mr Lin wondered if that was not a little like looking a gift horse in the mouth. Taiwan has developed a range of weapons on its own, often with US help, because many countries will not sell the island weapons due to Chinese pressure.

'Sometimes you can't have gifts from heaven,' the minister replied.

A Taiwan defence official, who declined to be identified, told Reuters that Taipei had alerted the United States to the fact they had shipped the wrong equipment over a year ago, but only this month received a reply asking for the parts back.

'It said on the side of the box it was batteries. Upon opening it was not what we had ordered. We didn't know what it was as we don't have that equipment, so we told the United States they'd sent over the wrong stuff,' the official said.

The incident has angered China, which views self-ruled Taiwan as its own, and Beijing has called for a thorough investigation, as well as an end to US arms sales to Taiwan.

The US has not had diplomatic relations with Taipei since 1979 but is bound by law to help Taiwan defend itself.

The erroneous fuse shipment was the Pentagon's second embarrassing misplacement of nuclear or nuclear-related equipment announced in recent months. An Air Force bomber mistakenly carried nuclear warheads over the United States in August 2007.

It was unclear what led to the fuse shipment, and the Pentagon said it does not yet know who was responsible.

The fuses, which send an electronic signal to the device that starts the nuclear weapon's trigger process, are among a class of sensitive equipment that must be accounted for on a quarterly basis.

Based on the information now known, the four fuses, which do not resemble helicopter batteries, were wrongly placed in an unclassified storage area. They were then shipped in late 2006 to Taiwan, which placed them in storage. -- REUTERS