In a letter to the Iranian president on Monday, the mothers of Shane Bauer, Sarah Shourd and Josh Fattal said, "We respectfully ask to meet with you when we visit Tehran and appeal to you to intervene to expedite the approval of our visa request. "We would be honored to tell you in person who our children are and why they do not deserve to continue to be held in detention without contact with the outside world."
The three hikers have been detained for more than 200 days, since they were apprehended after crossing the border into Iran from Iraq's northern Kurdistan region in July. Family members and friends say they crossed into Iran accidentally.
Cindy Hickey, Nora Shourd and Laura Fattal said the hikers have not been allowed to make a "single telephone call" or to write one letter since being held in Evin Prison.
"For more than three months we have no independent information about our children's physical health or their state of mind," the mothers wrote. "Their most recent consular visit from Swiss diplomats was on October 29. We asked an Iranian lawyer, Mr. Masoud Shafii, to represent our children out of respect for the Iranian judicial process, but he has been refused access to them."
Ahmadinejad proposed a swap of Iranians in U.S. prisons for the hikers earlier this month, but he did not cite specifics. In an interview with state TV, he said talks had been "under way to have an exchange, if it is possible."
"Recently they (the U.S.) have sent messages, we answered to bring them (the Iranians), to bring these people (the hikers)," Admadinejad said on Feb. 2. "We are hopeful that all prisoners will be released."
In December, Iran released a list of 11 Iranians it says are being detained in the United States, including a nuclear scientist who disappeared in Saudi Arabia and a former Defense Ministry official who was last seen in Turkey.
"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."
National Security Council spokesman Mike Hammer said U.S. officials had not entered into "any discussion" with Iranians authorities regarding an exchange.
Iran's foreign minister said in late December that Bauer, 27, Shourd, 31, and Fattal, 27, would be tried in court, but he did not indicate when a trial would begin or what charges would be filed. The hikers had earlier been accused of spying.
The hikers' mothers, meanwhile, said they "struggle to understand" they've been denied contact with their children — "young travelers whose only mistake appears to have been to lose their way on a hiking vacation."
"You too are a parent, Mr. President," the letter continued. "Surely you understand the depth of our distress, and the hopelessness we feel after appealing to you time and again to show our children the compassion they deserve, irrespective of the land of their birth. We hope you will look favorably on our request and restore our faith in human kindness."
Bauer's mother told Fox News they had not received any response from Iranian officials as of midday Monday and called for "movement of some kind" in the matter.
"No one independently has put their eyes on our children for over 100 days," Hickey said. "As a mom, I need to see that he's OK … We're fearing for their health."
Alex Fattal, Josh Fattal's brother, told FoxNews.com his relatives were "not doing well" on Monday.
"We're all praying," he said. "Nobody imagined it would go this long. It's been difficult."
The Associated Press contributed to this report.