PRESIDENT OBAMA yesterday called on Iran to immediately release the three U.S. hikers who have spent the last year in prison after reportedly crossing over the border while hiking in northern Iraq.

Iran has claimed the three are spies, but Obama said they have never worked for the U.S. government and are "innocent of any crime." He called their detention "unjust" and says releasing the hikers "is a humanitarian imperative."

The families of the three hikers were joined by about 75 supporters outside the Iranian mission to the United Nations yesterday in New York City, and Secretary of State Hillary Clinton again called for the hikers' release.

"Iran has long espoused to the world its commitment to justice, security and peace for all," she said. "We call on Iran to do the right thing and allow these three Americans to return home to their families."

Analysts and observers of the country don't know what it will take for Iranian authorities to release Josh Fattal, Shane Bauer and Sarah Shourd.

Gary Sick, a professor at Columbia University's School of International and Public Affairs, said it's possible the hikers are being used as bargaining chips.

"The hikers end up being the ones who end up paying the price for other people's actions," Sick said. According to Haleh Esfandiari, the director of the Middle East Program at the Woodrow Wilson International Center for Scholars in Washington, it will take international intervention perhaps by Turkey or Syria combined with keeping the hikers' story alive in the media to help get them released.

"You have to be very strong and not give into despair," said Esfandiari, who spent three months in 2007 in the prison where the hikers are held.

The recent return to Iran of nuclear scientist Shahram Amiri, who disappeared during an apparent pilgrimage to Mecca, Saudi Arabia, sparked some hope that the hikers would be released, but Sick believes the window of opportunity has passed.

The Iranian government accused the United States of kidnapping Amiri, but when he returned to Iran on July 15, Iranian media claimed he was working for Iranian intelligence.

"There was a lot of talk at the time that he was released that there was going to be a swap, but I think if it was going to happen it would have happened already," Sick said.

The Associated Press contributed to this report.