Iran will open its controversial enrichment plant to UN inspectors within two weeks and has agreed to export much of the uranium it has already enriched, the country’s chief nuclear negotiator told six countries meeting in Geneva.

The plans, tentatively agreed by Iran's Saeed Jalili, signify a temporary let up in a possible Iranian nuclear crisis, but representatives of the countries involved in the talks, including Britain and the US, warned that details were yet to be finalised.

Iran and the six countries, known as the E3+3, will meet again in a month’s time and no sanctions will be imposed until the details of the Iranian deal are negotiated.

EU foreign policy head, Javier Solana, who chaired the talks, said it was “the start of what we hope will be an intensive process".

But Iran could use the new agreement as proof that the world powers accept it has a right to enrich uranium and to pursue a nuclear program.

Under the new deal, up to three-quarters of Iran’s enriched uranium stock could be transferred to Russia and France, where it could be processed further and then used as fuel in a Tehran reactor for medical research.

The processing taking place outside Iran, would enrich the uranium enough to use as fuel for a reactor, but not enough to use as a nuclear weapon.