A spokeswoman for Zarif said Thursday's meeting indeed would mark the beginning of a "new era" in relations with the West.
Zarif was among the Iranian officials in the hall for Obama's address Tuesday. A U.S. delegation will be in the hall for Rouhani's speech, and the reaction will be closely watched. American officials sometimes walked out in protest during former Iranian President Mahmoud Ahmadinejad's fiery anti-American speeches at the annual U.N. meetings.
Rouhani's rhetoric has so far been more palatable to the U.S. But Obama warned Tuesday that it will take time to overcome the deep mistrust that has built up in the more than three decades since the U.S. and Iran broke off diplomatic relations.
"I don't believe this difficult history can be overcome overnight," Obama said. "The suspicion runs too deep. But I do believe that if we can resolve the issue of Iran's nuclear program, that can serve as a major step down a long road toward a different relationship, one based on mutual interests and mutual respect."
He added that in order for that effort to succeed, Iran's "conciliatory words will have to be matched by actions that are transparent and verifiable."
U.S. officials see Rouhani's election and more moderate stance as a sign of frustration among the Iranian public over international isolation and crippling economic sanctions. However, the Obama administration is unclear whether Rouhani is willing to take the steps it is seeking in order to ease the sanctions, including curbing uranium enrichment and closing the underground Fordo nuclear facility.
The U.S. is also seeking indications that Rouhani, as he pursues better relations with the West, has the backing of Iran's supreme leader, Ayatollah Ali Khamenei.
Obama has long said he is open to resolving the nuclear impasse with Iran through diplomatic channels, though he also has said in recent months that the window for that pathway is closing. Shortly after taking office in 2009, he exchanged letters with Khamenei, but their engagement quickly fizzled.
Obama again turned to letters this year to gauge Rouhani's appetite for diplomacy. The Iranian leader responded to Obama's outreach, setting the stage for their overlapping appearances at the United Nations.
Associated Press writers Edith M. Lederer and Darlene Superville contributed.
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