American officials also haven't ruled out meeting face-to-face with their Iranian counterparts to discuss disputes ranging from Iran's nuclear program to human rights and Syria's civil war. Secretary of State John Kerry and Iran's foreign minister will participate in a seven-nation meeting later this week about Iran's uranium enrichment activity. The U.S. and its allies fear Iran is trying to develop nuclear weapons, but the Islamic republic says its program is for peaceful energy production.
Hekmati's supporters are trying to ensure the 30-year-old's ordeal is included in the agenda of any potential U.S.-Iran contacts held this week in New York.
"We're just trying to do everything we can," Rep. Dan Kildee, D-Mich., the leader of the campaign, told The Associated Press. "If Rouhani is looking for a tangible step to demonstrate to the world his seriousness, this would be one."
Just hours after Rouhani's departure for New York, Iran declared Monday it freed 80 prisoners arrested in political crackdowns. The announcement appeared timed to boost the diplomatic potential of Rouhani's trip and promote his talk of outreach with the West.
But there was no news about Hekmati, or about two other Americans believed detained in Iran: Retired FBI agent Robert Levinson and Christian pastor Saeed Abedini.
Earlier this month, Hekmati wrote a letter to Kerry describing his "miserable prison conditions" and his belief that Tehran wanted to use him in a possible prisoner exchange.
Hekmati's letter was smuggled out of prison. His sister authenticated the handwriting. The State Department said it was trying to determine Hekmati's condition through Swiss diplomats in Tehran. No U.S. officials are based in the Iranian capital because the two countries don't have diplomatic relations.
Hekmati was born in Arizona and grew up in Michigan. He carries U.S. and Iranian passports.
His family says he traveled to Iran to visit his grandmothers when he was arrested in 2011.
Iran accused him of being a CIA spy, then tried, convicted and sentenced him to death. Iran's Supreme Court ordered a retrial last year, but he remains imprisoned.