Senior officials from the United States, China, Russia, Germany, France and Britain will hold a conference call on Thursday to discuss a third U.N. sanctions resolution against Iran over its nuclear program.
"This will be an opportunity for them to continue their discussions about issues related to the third Security Council sanctions resolution on Iran," said State Department spokesman Tom Casey.
The six held a conference call last week but failed then to agree on final elements of a resolution, which so far China and Russia have been reluctant to fully support.
Two rounds of sanctions have already been imposed on Iran for failing to heed a U.N. demand that it halt uranium enrichment, a process the West believes Tehran is trying to master so it can build atomic bombs.
Iran insists it wants only fuel for power plants and that it is not building a nuclear bomb.
However, Casey said it was unlikely the six major powers would agree on final language for a resolution.
"I don't think you will have an 'it's all done, let's go forward,' point coming out of this call," said Casey.
Earlier this month, a U.S. national intelligence estimate said Iran had stopped its nuclear weapons program in 2003, an announcement that raised questions over whether a third round of U.N. sanctions was needed against Iran.