By Paul Reynolds
BBC News Online world affairs correspondent
Iran denies it wants to build nuclear weapons
Iran is likely to be given an ultimatum that it must suspend all uranium enrichment activities or face being reported to the United Nations Security Council, according to senior British officials.
Speaking in advance of a board meeting of UN nuclear watchdog the International Atomic Energy Agency (IAEA) in Vienna on 13 September, the officials said: "At its last meeting in June, the IAEA laid out what Iran had to do and it has done only part of that."
"Iran has to give the international community the assurances we need and only a full suspension will do that."
However, any decision on going to the UN Security Council would not be taken at this meeting but at the following one scheduled for November.
The officials strongly implied that Britain would support reporting Iran to the council if it did not comply.
"It is a serious option which we would consider seriously," they said.
Iran's 'offer' dismissed
The US would prefer an immediate decision to go to the Security Council. But Britain, France and Germany, which have been acting together over Iran, believe that unity in the IAEA requires that Iran be given a final chance.
Iran previously agreed with the three European governments to suspend enrichment but has since said that this no longer applies.
The British officials dismissed reported Iranian offers this week to return to a policy of suspension.
"This kind of thing should not come days before an IAEA meeting," they said.
The officials also said Britain wanted to go beyond suspension and was demanding that Iran give up any ambitions to make fuel for a nuclear reactor.
This is also a position taken by the US and, the British officials suggested, was supported by France and Germany as well.
The reason for this is that once a country knows how to enrich uranium to make fuel, it could go on to enrich it further to make a nuclear bomb.
"We don't want Iran to develop any part of the fuel process," was the comment.
Such a demand goes beyond what is covered in the Nuclear Non-Proliferation Treaty (NPT). This does not ban a country from making fuel but says that it has to be under inspection.
The problem is that Iran has evaded inspections in the past and western governments now do not trust it.
The US has said publicly that it believes that Iran wants to make a nuclear bomb.
To get round the NPT Treaty, western governments would look to the UN Security Council to demand that Iran give up fuel enrichment as the only way to restore confidence in its peaceful intentions.
Iran has stated that it intends to develop fuel enrichment because it cannot rely on outside suppliers. It says that it has no intention of making a nuclear weapon.