The informal meeting will notably hear from Russian ambassador Vitaly Churkin, who travelled home this week to work out Moscow’s response to a draft resolution drawn up by Britain, France and Germany, they said.
The negotiations were suspended a week ago with Russia and China still deeply reluctant to agree to tough sanctions and Washington feeling the proposals from its European allies did not go far enough.
The draft calls for a series of nuclear- and ballistic missile-related trade sanctions, a freeze of assets related to Iran’s nuclear and missile programs and travel bans on scientists involved in those programs.
But it would allow Russia to continue building a billion-dollar nuclear power plant in the Iranian city of Bushehr — an exemption crucial to gaining Moscow’s approval for any resolution, diplomats said.
Iran faces sanctions after rejecting an earlier Security Council resolution requiring it to suspend a long-secret program to enrich uranium — a process that can eventually provide fissile material for nuclear weapons.
Tehran insists the program is only to provide fuel for civilian nuclear power stations.
The six powers — the five permament Security Council members plus Germany, which has close ties to Iran — have offered Tehran a package of economic and diplomatic incentives if it gives up the enrichment program.
US Secretary of State Condoleezza Rice called her five counterparts on Tuesday to urge speedy passage of the sanctions resolution and on Thursday warned that inaction was not an option.
"I think the Iranians are a threat and that’s why the international community’s got to be strong in resisting their ambitions," she said.
Rice also responded to the first launch by Iran earlier in the day of a new long-range ballistic missile, the Shahab-3, during war games seen as a warning to the West over the nuclear showdown.
"They’re trying to say to the world, ‘You’re not going to keep us from getting a nuclear weapon.’ The world has to say to them, yes, we will," Rice said in a radio interview.
"But the Iranians also I think are not unaware that the security environment is one in which if they actually were to do something, Iran would suffer greatly and so I think they probably understand that," she added.
But diplomats said there was still protracted and tough haggling to come as Russia and China remain reluctant to accept biting sanctions against a country with which they have close energy and trade ties.
The head of Russia’s national security council, Igor Ivanov, reaffirmed Russia’s reticence on the issue Thursday, warning that any Security Council decision "should be aimed not at punishing Iran but at continuing to resolve the problem through political means."
US officials have refused to elaborate publicly on their objections to the European draft, though the fact that Washington has so far not agreed to co-sponsor the measure is a clear sign that differences remain.
State Department spokesman Sean McCormack did say earlier in the week that Washington wanted firm guarantees that construction of the Bushehr power plant would not provide Iran with access to sensitive fuel-cycle technology.
But McCormack expressed confidence that the issues could be resolved and that the Bushehr project was not a deal-breaker.
"The bottom line is, at the end of these negotiations on a resolution, we believe we are going to get a good, strong resolution that sends a message to Iran that it must come into line with what the international community has demanded that they do," he said.