Vienna: Diplomats say Iran has formally responded to a nuclear fuel swap proposal but rejects the call to ship out most of the material it would need to make a warhead.

The draft plan would take most of Iran's stockpile of enriched uranium and return it in the form of fuel rods for its research reactor.

Iran needs the fuel to continue operating the facility, while the US and its allies would like to strip Tehran of its enriched material. That would delay its ability to make nuclear warheads, should it chose to do so.

The diplomats and a UN official spoke Tuesday on condition of anonymity because their information was confidential.