The draft text must first be approved by governments of the five Security Council members with veto power - the United States, Britain, France, Russia and China - as well as Germany, a European negotiator on the Iran controversy.
Western countries, which have been haggling with Russia and China on a text over the past two weeks, were optimistic of a deal a week ago only to see the talks drag on.
But two diplomats close to the negotiations told Reuters there was "provisional agreement" among the six.
If true, a vote could be scheduled for Monday after the full Security Council receives the draft.
Still, China's UN ambassador, Wang Guangya, has expressed frustration with US delays and its watering down of a council statement on the deaths of four UN peacekeepers in Lebanon, one of whom was Chinese.
He said difficulties remained on the Iran resolution because "not all members share the same view".
Tehran has vigorously objected to the resolution and says its nuclear activities are to produce electrical power only.
It has also indicated it might withdraw from the nuclear Non-Proliferation Treaty, if the resolution were adopted.
The draft is expected to demand Iran suspend all uranium enrichment-related and plutonium reprocessing activities as well as the construction of a heavy-water reactor.
It says that if Iran does not comply with the resolution, the council would consider measures under Article 41 of Chapter 7 of the UN Charter, which relates to economic and diplomatic sanctions. But it excludes military force.
The latest draft is under Chapter 7 of the UN Charter, Article 40, which says the council, before taking any action, can call on the those concerned to "comply with such provisional measures as it deems necessary".
Chapter 7 makes a resolution mandatory and provides options for enforcement. The date set for compliance is expected to be August 31.
Iran is building a heavy-water nuclear reactor at Arak, 190 kilometres southwest of Tehran. The US and European governments are concerned the plant's plutonium by-product will be used to produce nuclear warheads.