Six major powers meet here Saturday to mull a response to Iran's nuclear defiance but China is sending a lower-level diplomat in a signal of its reluctance to back tougher sanctions pushed by the West.
Britain, France, Germany, Russia and the United States are sending top officials of their respective foreign ministries at the meeting hosted by the European Union.
The six officials representing the so-called P5+1 were scheduled to meet from noon (1700 GMT) for a working luncheon at the EU mission in New York, but a diplomat cautioned against expecting any "spectacular" outcome.
Robert Cooper, a senior security adviser representing the EU, was to brief reporters at the end of the closed-door meeting around 2100 GMT.
US Secretary of State Hillary Clinton announced on Monday that the six would explore "the kind and degree of sanctions that we should be pursuing" as Iran doggedly refused to comply with UN demands to halt uranium enrichment.
Diplomats said Western members of the group of the five veto-wielding permanent members of the UN Security Council plus Germany were likely to present their Russian and Chinese colleagues with a range of new and tougher sanctions.
The goal is to crank up the pressure on Iran to accept a UN-brokered deal aimed at allaying suspicions about the nature of its nuclear program by shipping most of its low enriched uranium (LEU) stockpile abroad to be further enriched into reactor fuel.
But Tehran has ignored a US-set December 31 deadline to back the offer, drawn up by the UN International Atomic Energy Agency, and countered with its own proposal of a simultaneous and staged swap of LEU with reactor fuel.
Measures said to be under consideration include tougher sanctions targeting Iran's insurance, financial and arms sectors, diplomats said.
Washington favors sanctions targeting Iran's Revolutionary Guard Corps, seen as the economic and military backbone of the Iranian regime in a bid to minimize the impact on the Iranian people and avoid an adverse effect on the very people protesting President Mahmoud Ahmadinejad's hardline regime.
"Our goal is to pressure the Iranian government, particularly the Revolutionary Guard elements, without contributing to the suffering of ordinary (Iranians) who deserve better than what they are currently receiving," Clinton said early this month.
Washington and its Western allies fear that Iran is secretly developing fissile material for nuclear weapons under the cover of its uranium enrichment program.
But Iran insists its nuclear program is peaceful and solely geared toward generating electricity for its civilian population.
Washington along with Britain, France and Germany have for months sought to convince Russia and China that the time has come to get tougher with the Islamic republic, which has already snubbed its nose at three sets of UN Security Council sanctions.
Diplomats noted that Moscow, having seen its mediation efforts rebuffed by Tehran, has signaled it is prepared to turn up the heat on the Iranians.
But China, which has close economic and energy ties with Iran, has said new sanctions would be premature and that more time should be given for diplomacy to work.
Joining Cooper at the meeting will be Geoffrey Adams for Britain, Jacques Audibert for France, Emily Haber for Germany, Sergei Ryabkov for Russia, Williams Burns for the United States and Kang Yong, a counselor at China's UN mission, diplomats said.