Iran's Isfahan Uranium Conversion Facility
Iran's Isfahan Uranium Conversion FacilityAFP file

The United States expects Iran to reduce its stockpile of low enriched uranium to the levels required under an interim nuclear deal by a June 30 deadline, State Department spokeswoman Marie Harf said on Wednesday, according to Reuters.

"If they don't, that'll be a problem," Harf told reporters at her daily briefing, saying the Iranians had always gotten to the prescribed levels under interim nuclear deals.

"We expect that they will," she stressed.

Under an interim nuclear deal struck in November of 2013 and renewed the following year, every six months Iran must reduce its stockpile of low enriched uranium (LEU) that is enriched to a purity of up to five percent, to a maximum of about 7,650 kg.

But according to the latest report of the UN’s nuclear watchdog, the International Atomic Energy Agency (IAEA), Iran has about 8,714.7 kg of low enriched uranium. If refined much further, enriched uranium can provide fuel for nuclear weapons.

Harf said Iran's LEU stockpile had gone up and down and but that it had always gotten back to the 7,650 level by previous deadlines, as required. Under a subsequent agreement struck on April 2, Iran must eventually cut the stockpile to 300 kg.

The New York Times, which on Tuesday reported on Iran's having increased, rather than decreased, its stockpile of LEU in recent months, said the rise posed a major diplomatic and political challenge to the United States.

On Tuesday, Harf had responded to The New York Times report by saying she was “perplexed” by it, and stressing that Iran’s increased stockpiles of LEU have not complicated the current negotiations.

Iran and the six world powers are holding ongoing discussions aimed at turning a preliminary deal into a permanent one by a June 30 deadline.

The sides made a major breakthrough at talks with Iran on April 2 by agreeing on the parameters for a final deal to scale back its nuclear capabilities, but still have a series of technical issues to resolve by the looming deadline.

Iran has for years declared that it will never give up on what it sees as its “right to enrich uranium” as part of a deal with the West.