Iranian President Mahmoud Ahmadinejad on Tuesday proposed a swap of Iranians in U.S. prisons for three American hikers being held in Tehran.

Ahmadinejad said in an interview with state TV that negotiations were taking place about exchanging the hikers for several Iranians jailed for years in the United States.

"We are hopeful that all prisoners will be released," he said.

These file photos released by freethehikers.org show, from left, Joshua Fattal, Shane Bauer and Sarah Shourd. The three were arrested in Iran last July. (freethehikers.org/Associated Press)

Ahmadinejad did not mention specifics but in December, Iran released a list of 11 Iranians it says are being held in the U.S. — including a nuclear scientist who disappeared in Saudi Arabia and a former Defence Ministry official who vanished in Turkey. The list also includes an Iranian arrested in Canada on charges of trying to obtain nuclear technology.

"I had said I would help in releasing them, but the attitude of some U.S. officials damages the job," Ahmadinejad said. "There are a large number of Iranians in prison in the U.S. They have abducted some of our citizens in other countries."

Shane Bauer, Sarah Shourd and Josh Fattal were hiking in Iraq's northern Kurdistan region in July when they accidentally crossed the border into Iran, their families have said.

Samantha Topping, a New York City-based spokeswoman for the three families, said they had no comment on Ahmadinejad's remarks.

The White House, through a spokesman, called the reports "fragmentary."

"If President Ahmadinejad's comments suggest that they are prepared to resolve these cases, we would welcome that step," National Security Council spokesman Mike Hammer said.

"But we have not entered into any discussion with Iran about an exchange. As we have indicated publicly, if Iran has questions about its citizens in U.S. custody, we are prepared to answer them."

Iran's foreign minister said in late December that the three would be tried in court, but he did not say when a trial would begin or what the three would be charged with other than to say they had "suspicious aims." Earlier, the country's chief prosecutor said they were accused of spying.

Their families have said that's ludicrous and last month hired an Iranian attorney to press the case.

Ahmadinejad said there were "indications they knew they were crossing into Iran."

The last time anyone sympathetic saw the three was at the end of October, when Swiss diplomats were granted a short visit. The U.S. has no diplomatic relationship with Iran and is represented in such matters by the Swiss. At the time, the diplomats said the three were in good health.

When the list of 11 Iranians came out, State Department spokesman P.J. Crowley said it appeared the Iranian government was trying to suggest some kind of equivalence between the hikers and Iranians that had left Iran.

"There really is no equivalence at all," he said at the time.

Three of the Iranians on the list have been convicted or charged in public court proceedings in the United States. The circumstances surrounding some of the others are more mysterious.

Ali Reza Asgari, a retired general in the elite Revolutionary Guard and a former deputy defence minister, disappeared while on a private trip to Turkey in December 2006.

Shahram Amiri, an Iranian nuclear scientist, went missing while on a pilgrimage to Mecca in Saudi Arabia in June. Iran's foreign minister has accused the U.S. of helping to kidnap him and has asked for his return.

The list also includes three Iranians who Tehran claims were abducted in Europe and sent to the U.S.: merchant Mohsen Afrasiabi, who it says disappeared in Germany, as well as electrical engineering student Majid Kakavand and a former ambassador to Jordan, Nasrollah Tajik, who it says vanished in France.

One of the Iranians, Mahmoud Yadegari, was arrested in April in Canada after a joint investigation with the U.S. Department of Homeland Security and charged with trying to send nuclear technology to his native Iran.

Authorities allege Yadegari tried to procure and export pressure transducers, which can be used in the production of enriched uranium but also have many legitimate commercial uses.