The United States and China have agreed on the need for Tehran to respond positively to existing nuclear proposals by the major powers ahead of a meeting Thursday between Iran and the five permanent U.N. Security Council members and Germany.
A U.S. official said both Washington and Beijing "believe that Iran should cooperate with the P5+1," referring to the United States, Britain, France, China, Russia and Germany.
World leaders from the group hold nuclear talks Thursday with Iran's top diplomat, amid signs Tehran is looking to negotiate a settlement over its controversial nuclear program.
Most analysts do not expect a breakthrough at the meeting, but diplomats hope to agree on a restart of the P5+1 nuclear talks, which were last held in April.
The meeting will mark the highest level interaction between Washington and Tehran in six years and will be one of the very few times senior officials from both countries have met since diplomatic ties were severed in 1980.
U.S. Secretary of State John Kerry and his Iranian counterpart Javad Zarif will attend, as will foreign ministers from Britain, France, China, Russia and Germany. European Union foreign policy chief Catherine Ashton will host the talks.
The high-level discussions follow a proposal by Iranian President Hassan Rouhani, addressing a U.N. General Assembly meeting on disarmament, for a comprehensive treaty banning all nuclear weapons.
Describing nuclear disarmament as Iran's "highest priority," Rouhani called for Israel to join the Non-Proliferation Treaty and put its widely suspected nuclear arms under international control.
The Iranian leader told The Washington Post Wednesday he wants a deal on his country's nuclear program in three to six months, saying the "only way forward" is for a timeline to be inserted into the talks.
Dina Esfandiary with the Non-Proliferation and Disarmament program at the International Institute for Strategic Studies told VOA such a timeline is unrealistic, given the obstacles to overcome.
"But having said that, the fact that he is pointing out such a short timeline is in itself quite positive, because it means the Iranians are going to willing to really throw everything they have at these negotiations," Esfandiary said.
Esfandiary said Rouhani's rapid timeframe for reaching a deal could reflect domestic pressure from those in Iran's government who are skeptical of improved relations with the West.
"It's likely the timeline has more to do with Rouhani's position inside Iran more than anything else," she speculated, "because that will be the time he has before the conservatives in Iran start to ask him questions about whether he has been able to deliver."
Though Iranian officials have made weeks of conciliatory gestures to the United States, it is unclear what, if any, concrete proposals the Iranian delegation is prepared to offer regarding its nuclear program.