The European Union says it is studying a call by Iran for the resumption of nuclear talks.
Iran insists that its nuclear energy programme is peaceful
The call came on Sunday in a letter from chief Iranian nuclear negotiator Ali Larijani to the foreign ministers of France, Germany and Britain.
It follows the breakdown of talks in August, when Iran defied international calls and restarted uranium conversion.
UK Foreign Secretary Jack Straw said he and his colleagues had looked at the letter very carefully.
A recent International Atomic Energy Agency (IAEA) resolution paved the way for the referral of Iran to the United Nations Security Council for non-compliance with its nuclear commitments. However, the agency did not set a date for this.
The US and other countries say Iran is pursuing a covert nuclear weapons programme. Iran says its nuclear activities are aimed solely at generating nuclear power.
"The Iranians are under the obligation to respond positively to the resolution of the board of governors at the International Atomic Energy Agency (IAEA) in late September and we look to them to do that," said Mr Straw.
The three European powers - the UK, France and Germany - have led talks with Tehran on behalf of the EU.
The talks have been on the basis of the suspension by Iran of its uranium conversion activities. These were resumed in August under new hardline President Mahmoud Ahmadinejad.
The letter from Mr Larijani, the secretary of Iran's Supreme National Security Council, was handed to the ambassadors of the UK, France and Germany on Sunday.
According to Iranian news agencies, Mr Larijani said in the letter that Iran would "welcome negotiations that are constructive and based on logic".
But the letter is reported to insist on "Iran's need to exercise its legitimate rights and to see its national interests guaranteed".
It is the first approach that Mr Larijani has made to the EU powers since taking over the nuclear portfolio after Mr Ahmadinejad became president in June.
Mr Ahmadinejad's recent call for Israel to be "wiped off the map" provoked international outrage.