Ambassadors from Germany and the UN Security Council's five permanent members were to hold another round of informal talks on a European draft resolution mandating nuclear and ballistic missile-related sanctions against the Islamic republic.
The tough sanctions, which include travel bans and financial restrictions on Iranian scientists working on the nuclear and missile programs, have been the subject of several exploratory meetings among the six envoys. But the hard bargaining to agree a text has yet to begin, diplomats said.
The draft would also allow Russia to continue building a one-billion-dollar nuclear power plant in the Iranian city of Bushehr -- an exemption seen as crucial to efforts to secure Moscow's approval.
But Russia and China, which both have significant energy and trade ties with Tehran, view the European draft as too tough and unlikely to bring about Iranian co-operation.
The Russians have offered amendments that would drastically reduce the scope of the sanctions proposed by France, Britain and Germany, the three countries that led inconclusive efforts to coax Iran into scaling back its nuclear ambitions.
But the United States is pushing for even tougher sanctions that are even more unacceptable to Moscow and Beijing.
Monday's meeting follows top Iranian nuclear negotiator Ali Larijani's two days of talks with Russian leaders in Moscow on the Iranian nuclear issue.
After Larijani's talks with President Vladimir Putin on Saturday, Russian Foreign Minister Sergei Lavrov said Iran would continue to study a package of economic and security incentives offered by the six powers if Tehran agrees to halt uranium enrichment.
"Iran has responded to these proposals and we think that in showing its good will, there is a possibility, beginning with the proposals of the Six and taking Iran's response into account, to find an acceptable basis for talks to restart," Lavrov said.
"In the days ahead, we will continue our contacts with the Six, which have proposed to Iran ideas which serve as the basis for the beginning of negotiations," Interfax quoted the Russian minister as saying.
After two round of talks last week, France's UN Ambassador Jean-Marc de La Sabliere said the six powers were trying to understand each other's positions before moving to narrow their differences.
His Russian counterpart Vitaly Churkin said that the sponsors of the draft "have been listening to our explanation and we have been listening to their rationale."
"It would be an exaggeration to say we are close to each other," he added. "But we do have a mandate (from our ministers) to agree on a resolution. Our premise is the unity of the Security Council. In light of the Russian amendments, we have a good basis for that."
The Russians want the sponsors of the draft to remove the travel ban and assets freeze and drop any reference to Bushehr.
The Russian and Chinese envoys also indicated that they differ with their four western counterparts about what type of sanctions were agreed at the ministerial level meeting of the six powers last summer if Tehran refused to comply with the demand for a uranium enrichment freeze.
Iran has defiantly spurned an August 31 Security Council deadline to halt its uranium enrichment program -- a process that can lead to the production of fissile material for nuclear weapons.
Tehran insists its nuclear program is peaceful and aimed at generating electricity.

Copyright AFP (Agence France-Presse), 2006