Iran will start dismantling parts of its uranium stockpile next week after details of an interim deal on its nuclear programme were finalised over the weekend.
In a move described as "concrete progress" by Washington, the small print of the agreement has now been nailed down between Tehran and negotiators representing Russia, China and the Western powers.
Iran first said all outstanding disagreements had been resolved on Saturday, but Washington's confirmation came only yesterday. William Hague, Britain's Foreign Secretary, hailed it as an important "first step".
The process of dismantling Iran's stocks of enriched uranium, which the West suspects were intended for weapons use, will begin next Monday. More frequent inspections by international monitors are also planned.
"Beginning January 20th, Iran will for the first time start eliminating its stockpile of higher levels of enriched uranium and dismantling some of the infrastructure that makes such enrichment possible," the White House said. Under the agreement, which follows a landmark deal reached in November, Tehran will halt parts of its enrichment programme for six months in exchange for modest relief from the international sanctions that have crippled its economy.
President Barack Obama also said he would veto plans to pile on yet more sanctions, which have been proposed by hawkish factions in the House of Representatives. They claim the deal takes too much pressure off the Iranians and will reduce their incentives to abide by it. A bipartisan sanctions bill tabled before Christmas has attracted 59 out of 100 senators as co-sponsors. In all 67 are needed to over-ride the presidential veto.
The six-month moratorium agreed to by Iran is designed to give further negotiating time for a longer-lasting settlement. Opponents of the deal, including Israel, suspect Tehran is simply playing for extra time to perfect its nuclear programme.
Several sticking points also remain, including whether Iran will dismantle bomb-proof nuclear plants suspected to have been built purely for military purposes.
Recognising the ongoing concerns, Obama said: "I have no illusions about how hard it will be to achieve this objective, but for the sake of our national security and the peace and security of the world, now is the time to give diplomacy a chance to succeed."
Iran will receive a US$550 million ($660 million) instalment of US$4.2 billion in blocked funds under a six-month landmark nuclear deal with the West.
- additional reporting AFP