Iran has warned Britain that relations will suffer if a former Iranian diplomat is not freed from prison in Britain.
Iran is also seeking the release of two Iranian film makers it says are being held by British forces in Iraq.
The former Iranian diplomat, Hade Soleimanpour, was arrested at the request of Argentina, which accuses him of masterminding the bombing of a Jewish centre in Buenos Aires, when he was ambassador there in 1994.
He was detained in Durham, where he was studying for a doctorate. Mr Soleimanpour was refused bail earlier this week after a judge ruled that he might leave the country.
The warning was given by Kamal Kharrazi, the Iranian Foreign Minister, in a phone call to Jack Straw, the Foreign Secretary. The call was reported by state-run Tehran television.
"The continued detention of Soleimanpour and the two documentary film makers will leave very destructive effects on the two countries' relations," Mr Kharrazi was quoted as saying. "The Islamic Republic of Iran is sensitive about the fate of its nationals."
Iran has already taken the first step to downgrading diplomatic relations by recalling its ambassador. Officially, the ambassador has been recalled for consultations, but officials on both sides have conceded he may not return.
The British embassy in Tehran has been closed since Wednesday after shots were fired at it from a passing motorcycle. The Foreign Office in London announced on Thursday that non-essential staff and dependants were being allowed to leave the country if they chose. It stressed that there was no general evacuation of British diplomats and no reason for anyone planning to travel to Iran not to do so.
The Foreign Office insisted that there was no downgrading of relations. Richard Dalton, the ambassador, remains at his post. Over the past year and a half, Britain has made great efforts to improve relations with Iran. Yesterday's warning appears to reflect the view that London would have more to lose from a downgrading of relations.
¿ Washington has abandoned plans to report Iran to the UN Security Council for what it says are breaches of UN nuclear rules, despite worries that Tehran is developing nuclear weapons. Diplomats said on Thursday there was little support for a draft resolution the US had sent to the UN's International Atomic Energy Agency.Reuse content