American officials say Rouhani's change in tone is driven by the Iranian public's frustration with crippling economic sanctions levied by the U.S. But it is still unclear whether Iran is willing to take the steps the U.S. is seeking in order to ease the sanctions, including curbing uranium enrichment and shutting down the underground Fordo nuclear facility.
State Department officials said Kerry would seek to answer that question on Thursday when new Iranian Foreign Minister Mohammad Javad Zarif joins nuclear talks between the U.S. and five other world powers. Zarif's participation, which was announced Monday, sets up the first meeting in six years between an American secretary of state and an Iranian foreign minister, though it's unclear whether the two men will break off from the group and hold separate one-on-one talks.
Catherine Ashton, the European Union's foreign policy chief, told reporters after meeting with Zarif that she saw "energy and determination" for talks to move ahead with the U.S., Russia, China, Britain, France and Germany.
On Twitter, the U.S.-educated Zarif called his meeting with Ashton "positive," and he added, "Need new start under new circumstances."
The prospect of bilateral talks between Kerry and Zarif did little to tamp down speculation about a meeting between the U.S. and Iranian presidents, who both arrived in New York on Monday. The most obvious opportunity for a direct exchange appears to be at a U.N. leaders' lunch both are scheduled to attend on Tuesday.
But a lunch meeting would put Obama in the risky position of engaging Rouhani before knowing what the Iranian leader will say during his highly anticipated address to the U.N. General Assembly. Rouhani is scheduled to speak late Tuesday afternoon, while the U.S. president will address the U.N. in the morning.