A senior Iranian nuclear official on Tuesday dismissed US concerns over the purchase of new components reportedly destined for a controversial reactor.

Behrouz Kamalvandi, spokesman for the Atomic Energy Organisation of Iran (AEOI), said he had "no information on (the reported) purchase" of illicit parts for the Arak heavy water nuclear complex.

Online magazine Foreign Policy reported this week that the US had privately told a UN panel of experts monitoring sanctions that Iranian agents sought to illicitly obtain parts for the Arak complex.

Asked about the report, State Department spokeswoman Jen Psaki said it was "not breaking news" that Washington was "concerned about Iran's procurement activities".

But she insisted that "Iran has kept all of their commitments" made as part of an interim deal on its nuclear programme reached in November 2013.

Under that accord, Iranian leaders agreed to freeze parts of their nuclear enrichment programme in return for the release of billions of dollars in frozen oil revenues.

Despite a further year of negotiations, the group known as the P5+1 which includes the United States failed to seal a full deal by a November 24 deadline.

They have extended the deadline for talks until June 30.

Kamalvandi said Iran was keeping its side of the interim deal.

"Even if there had been a purchase, that would not contravene the Geneva accord or the seven months extension" of talks, Kamalvandi told reporters.

"It was concluded in Geneva that we would not install new (nuclear) hardware," he said.

Iran's nuclear chief Ali Akbar Salehi last month ruled out further negotiations on the design of the Arak reactor that the West fears could be used to produce plutonium for an atomic bomb.

It remains one of the main issues in the nuclear talks, with Iran insisting the unfinished reactor, located 240 kilometres (145 miles) southwest of Tehran, is solely for research purposes.