US Under Secretary of State for Political Affairs Nicholas Burns told reporters that the six powers would meet Wednesday and Thursday, following "constructive talks" which he chaired last week in Washington.
At Friday’s four-and-a-half-hour talks, political directors for the six countries’ foreign ministries "discussed the elements of a third resolution" of sanctions, Burns said, but "we did not come to an agreement."
"We said we would continue those talks again on Wednesday and Thursday of this week, leading up to the ministerial meeting" on the issue scheduled for Friday on the sidelines of the UN General Assembly. "Probably both days," he added.
The United Nations Security Council has passed three resolutions against Iran, two of them imposing sanctions after Iran refused to heed its ultimatums to suspend uranium enrichment.
The six powers — the Security Council’s permanent members China, France, Russia, Britain, the European Union and the United States, plus Germany — are now mulling US proposals for further measures, amid ongoing defiance by Tehran.
Iran vehemently rejects the US charges it is seeking an atomic weapon, saying the nuclear drive is aimed solely at generating energy for a growing population.
Enriching uranium is normally a key component of the cycle to make nuclear fuel but in highly-enriched form the uranium could be used to make the fissile core of a nuclear bomb.
Iran has been enriching uranium to levels well below that required to make nuclear weapons.
Burns earlier said Friday’s talks were "serious and constructive" and the political directors discussed elements of a new Security Council resolution, "as well as possibilities of continued dialogue with Iran."
"We are very hopeful," Burns said Monday, "and we hope for progress in a relatively short period of time."