Russia has turned up the pressure on its nuclear ally Iran
Russia is to stop exporting nuclear material to Iran following its refusal to sign up to an international protocol, a senior British official has said.
The official said President Vladimir Putin had announced to other leaders at the G8 summit in France that his country would halt "all nuclear exports" until Iran signed up to tougher nuclear inspections.
It follows a decision by the G8 leaders to issue a joint statement describing weapons of mass destruction as the "pre-eminent threat" to international security.
The statement also calls on North Korea to dismantle "visibly, verifiably and irreversibly" its nuclear weapons programme.
On Sunday, Russia - Iran's main partner in its nuclear power programme - added its voice to those calling on Tehran to sign an additional protocol to the nuclear non-proliferation treaty.
That would permit tougher international inspections, giving the Iranians a chance to prove they were not trying to produce nuclear weapons.
But Iran refused to agree to this.
An Iranian foreign ministry spokesman, Hamid-Reza Asefi, said Iran would not sign any new protocols until international sanctions were dropped and it was given the technology to develop atomic energy for peaceful purposes.
Mr Asefi said Iran was allowed such technology under the non-proliferation treaty it had already signed.
He said American contractors should help build Iran's nuclear power stations if they really were concerned about Iranian intentions - an offer immediately rejected by US officials.
Iran had appeared to be confident of Russian support to finish its nuclear reactor at Bushehr - the facility at the centre of American concerns - following Mr Putin's meeting with US President George W Bush in St Petersburg.