"We've made substantial progress," Emyr Jones Parry told reporters after envoys of the six nations held two hours of informal talks here.

"Our expectation now is that the fruit of our discussion will be sorted out by our experts this evening, sent back to our capitals and we will meet again tomorrow morning to see how we take it forward," he added.

The two-hour informal session involving envoys of the UN Security Council's five permanent members (P5) -- Britain, China, France, Russia and the United States -- plus Germany followed up on bargaining sessions they held throughout last week.

Jones Parry said the P5 would be able to report Tuesday their progress to the Security Council's 10 non-permanent members.

The six are considering new punitive measures, including a travel ban on officials involved in illicit nuclear work, an arms embargo as well as financial and trade restrictions, to tighten sanctions adopted by the council last December in the face of Tehran's nuclear defiance.

Last week, China and Russia voiced reservations about the travel ban, the trade restrictions and a proposal to extend an assets freeze to "entities, owned or controlled by the Iranian Revolutionary Corps (IRGC)." They also objected to preventing any technical help to entities involved in Iran's nuclear and missile programs.

"There are some last-minute details which need to be worked out ... We're quite close," Russian Ambassador Vitaly Churkin said late Monday.

"Fundamentals have been worked out ... but the devil is in the details. There are no main sticking points, but three or four details have to be finalised."

His Chinese counterpart Wang Guangya said the financial and trade restrictions had been dropped from the text.

"We've made overall good progress. I don't want to raise expectations because we're all reporting back to capitals," said US acting ambassador Alejandro Wolff.

"There are things that we're very pleased about. There are things that we are less pleased about and likewise probably with the other delegations involved," he added. "We'll have to wait and see if the package is something that the capitals can agree to."

"I think we are now very close," French Ambassador Jean-Marc de La Sabliere said. "This is the best meeting we have had since the beginning of the negotiation."

"What we want is that Iranians understand they have a choice. The door is always open," he noted.

"We hope this resolution will make them think twice and that they will come back to what we all expect ...that they (will) suspend their enrichment and reprocessing activities."

German Ambassador Thomas Matussek concurred.

"I find it a very encouraging experience that the six tried to work together in a very constructive and forward-looking way, and that signals that the security council ...is together because we need that in order to get Iran back on the negotiating track," he said.

"That is what we want. It's not punishing, it's not harming Iran, but to get them back on track and to help them find a way out of their self-imposed isolation," the German envoy added.

The six powers have offered to suspend their sanctions against Iran if Tehran complies with UN demands, particularly by suspending its sensitive nuclear fuel work.

Tehran has so far refused to suspend a uranium enrichment program the West fears is a cover for producing nuclear weapons. It insists its goal is simply to provide fuel for electricity generation.

In a bid to forestall further sanctions, Iranian President Mahmoud Ahmadinejad offered over the weekend to defend Iran's position in person when the full Security Council meets to discuss the sanctions draft.

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