Exasperated by Iran's refusal to free or try their sons, the mothers of American hikers Josh Fattal and Shane Bauer, imprisoned since 2009, were to begin an unusual hunger strike Thursday.

Laura Fattal, 58, of Elkins Park, and Bauer's mother, Cindy Hickey, 50, of Minnesota, say their fast is in "solidarity with Josh and Shane," who also may have stopped eating as a form of protest.

Supporters of the hikers say Fattal, an environmental activist, and Bauer, a photojournalist, both 28, were trekking in Iraqi Kurdistan when they were arrested by Iranian border guards on July 31, 2009, and charged with espionage, which the pair strenuously deny. The case was to go to trial May 11 but was halted without explanation when Fattal and Bauer were not brought to court.

Although the mothers don't know for sure because their sons are not allowed even to see their Iranian lawyer, they believe the men are striking now to protest the delay.

"We truly believe Josh and Shane are on hunger strike," Laura Fattal said. "Why are [the authorities] hiding the kids from us? Why didn't they have the trial? Why are they holding them on baseless charges?"

Josh Fattal's brother, Alex, 32, called the strike beginning Thursday "a relay, or rolling strike," in which "different people will go as long as they can." A spokeswoman for the families said the mothers were expected to end their strike Saturday and "hand off" the fasting to other supporters, who would attempt to keep the matter in the public eye.

Contact staff writer Michael Matza at 215-854-2541 or mmatza@phillynews.com.