The error was only discovered last week.
The 55cm-long fuses, which reportedly bear no similarity to helicopter batteries, have since been returned to the US.
Robert Gates, the US defence secretary, has ordered an urgent investigation into the error and a through review of policies and procedures related to the country's nuclear weapons, a senior Pentagon official told reporters on Tuesday.
"Those who are responsible will be held accountable," said Ryan Henry, principal deputy undersecretary of defence for policy. "The secretary is quite forceful on this."
China, which strongly opposes US arms sales to Taiwan was also informed of the error, he said.
"Our policy on Taiwan arm sales have not changed. This specific incident was an error in process only and is not indicative of our policies, which remain unchanged," Henry said.
"Our policy on Taiwan arm sales have not changed"
US principal deputy undersecretary of defence for policy
The US, which is Taiwan's main arms supplier, insists that it only sells weapons to Taiwan that would allow the self-ruled island to defend itself.
China and Taiwan split following a civil war in 1949 but Beijing continues to claim the island as part of its territory and has threatened to attack if Taiwan formalises its independence.
It also has about 700 missiles pointed at the island.
It is not yet clear whether the mistaken shipment constitutes a violation of any treaty or agreement governing sales of missile technology, but Henry insisted any such violation was unintentional.
"We are being transparent. We have corrected the situation," he said, admitting that the error was "disconcerting".
|Ryan Henry demonstrates the |
positioning of the nuclear fuses [AP]
Speaking to reporters, Henry said that in an organisation the size of the US military, mistakes would be made, but that such errors could not be tolerated when they fall in the area of nuclear-related weapons systems.
He said the nose cone and fuse systems were classified but the technology they use dates from the 1960s.
However, Hans Kristensen, an expert at the Federation of American Scientists, told the AFP news agency that the fuses, even if dated, were "hugely important" nuclear weapons components.
"For a country like China, that is trying to develop more capable systems, that would be very important material to get. And (for) any country that is even lower on the nuclear threshold scale, having not quite gotten there, would be potentially even more important."
US officials said there was no indication the fuses had been tampered with.
The incident was the second major nuclear security breach in less than a year.
|Last year nuclear-armed missiles were |
mistakenly flown across the US [AP]
Last October it emerged that six nuclear-armed cruise missiles had been flown across the US attached to the wing of a B-52 bomber. The crew were not aware they had been carrying nuclear weapons.
An investigation concluded that the mistaken transfer had resulted from "a series of procedural breakdowns and human errors," Pentagon officials later admitted.
In the Taiwan case officials said they did not know as yet how it took so long for the error to have come to light.
The fuses are supposed to be subject to quarterly inventory inspections.
But instead the mistake was only revealed last week following months of discussion with Taiwanese authorities over the missing helicopter batteries they had ordered.
The fuses involved do not themselves contain nuclear material but are housed in the nose cones fitted to nuclear warheads on Minuteman intercontinental ballistic missiles.
They are used to ignite the trigger which then detonates the warhead.