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Alex Fattal says his brother Josh is a "very resilient guy," an environmentalist who taught sustainable living skills while in the United States. But for the last two years, Josh Fattal's own survival has been tested as he remains in an Iranian prison on charges of espionage.

Josh Fattal and Shane Bauer, both 29, have been detained since July 2009, when they were arrested by Iranian forces on the country's unmarked border with Kurdistan as they hiked during a vacation. A third hiker, Bauer's fiancée Sarah Shourd, 33, was also arrested but was released in September 2010 after 410 days in solitary confinement. She has refused to return to Iran for trial.

On Friday, two days before the men are due to have their final hearing in an Iranian court on espionage charges, supporters of Fattal and Bauer will hold a rally demanding their release outside the Iranian Mission to the United Nations in New York City.

"We just want to send a very clear message that we are ready for this to be over," Alex Fattal told FoxNews.com. "The theme is two years too long -- they never should've been detained in the first place."

Both men deny the charges, claiming they were only hiking in a scenic area near northern Iraq. Their attorney, Masoud Shafiei, told The Associated Press last month that he had been notified of the July 31 hearing, but added that he had not been able to meet with Bauer and Fattal in recent months and hoped to do so prior to the hearing.

"Knowing Josh, he's a very resilient guy," Alex Fattal said. "But this is a test that nobody should have to endure. Two years in isolation is very difficult. Many people in the mental health field say this type of isolation can cause long-term psychological damage, so we're worried."

In May, relatives of Bauer and Fattal said the men called their families by telephone -- the first phone call since last November.

"That's a long time ago," Alex Fattal said. "We continue to be very worried about them. This has taken a terrible toll on our families and on Josh and Shane."

Iranian authorities have said they expect to make a final decision in the case by late August. But that's simply not good enough for Alex Fattal, who wants the family's "nightmare" to end immediately.

"The only thing that's clear is they're innocent and they have a lot to contribute to this world," he told FoxNews.com. "It's time for our families to be whole again. There's absolutely no reason for this nightmare to continue. Hopefully on Sunday, that'll be the case."