President Mahmoud Ahmadinejad, who appeared to be trying to get them released in time for his arrival at the U.N. General Assembly, also left Monday for New York empty handed. Complicating the $1 million bail-for-freedom proposal is a deepening internal rift between the president and the country's ruling clerics, who control the courts.
Ahmadinejad's rivals in Iran might be seeking to hold up the deal in part to deprive him of the chance to claim credit on the world stage for the release of the Americans, Shane Bauer and Josh Fattal, who were arrested in July 2009 along the Iraq-Iran border.
A statement by the interfaith delegation from the U.S. said they urged Ahmadinejad and other officials to release the two men, both of them 29 years old, on humanitarian grounds during their weeklong visit, which they said came at Ahmadinejad's invitation.
Iran's courts have considered a deal to set aside the men's eight-year prison sentences and release them on $500,000 bail each. But the hard-line judiciary has not given any timetable for a possible release.
Last September, a third American who had been arrested with them, Sarah Shourd, was released after a similar bail payment and a nearly identical tussle between the president and his rivals in the judiciary.
The three Americans - friends from their days at the University of California at Berkeley - deny the charges. Their families say they were just hiking in northern Iraq's scenic and relatively peaceful Kurdish region when they may have accidentally strayed over the unmarked border with Iran. Iran has accused them of spying for the United States.
The official explanation for the delay in their possible release is that a second judge needed to sign the bail papers was on vacation until Tuesday, according to their lawyer, Masoud Shafiei.
Last week, Ahmadinejad suggested a deal to free them could be on the fast track, and the Gulf nation of Oman appeared to be acting as a mediator, as it had with Shourd.
However, Iran's judiciary - directly controlled by Supreme Leader Ayatollah Ali Khamenei - quickly slapped him down with a blunt reminder that only the courts have the authority to set the ground rules and timing on a possible release.
More mixed signals followed.
Iran's foreign minister, Ali Akbar Salehi, said the courts were willing to commute the Americans' sentences in the "near future" as a gesture of Islamic mercy. But Mohammed Javad Larijani, the head of Iran's Human Rights Council and a brother of the powerful judiciary chief, said the men's "crime was not limited to illegal trespassing." They were spying, he said, and "we do not reward spies."
U.S. Secretary of State Hillary Rodham Clinton said Thursday the United States continues to hope the Americans will be released, adding that Washington has received word through a number of sources that the two will be returned to their families.
The last direct contact family members had with Bauer and Fattal was in May 2010 when their mothers were permitted a short visit in Tehran.
Since her release last year, Shourd has lived in Oakland, California. Bauer, a freelance journalist, grew up in Onamia, Minnesota and Fattal, an environmental activist, is from suburban Philadelphia.
Bauer proposed marriage to Shroud while in prison.
Surk reported from Muscat, Oman.