She's thought "long and hard" about returning for her trial, but was "not in a position to make that decision" because her mother just had gallbladder surgery, she told supporters in Oakland, Calif.
Shourd, 32, her fiance Shane Bauer and friend Joshua Fattal, both 28, were detained by Iranian border guards July 31, 2009, while hiking in Iraqi Kurdistan. Iran claimed the three crossed into Iranian territory and were spying for the United States, which they and the U.S. State Department denied.
The three University of California, Berkeley, graduates claimed they were kidnapped from within Iraq.
Iran charged the three with espionage and planned to begin their trial Saturday. The trial was postponed until Shourd returned to face the charges, Iranian judiciary spokesman Gholam Hossein Mohseni-Ejei said Monday.
Shourd was released from Iran's Evin Prison on $500,000 bail Sept. 14 after her mother announced her daughter had discovered a lump in her breast.
Shourd urged supporters worldwide Wednesday night to create banners calling for Bauer and Fattal's freedom.
The banners would be a "symbolic bridge that can reach across social, cultural and geographical barriers with a message of hope and freedom," the Oakland Tribune quoted Shourd as saying.
"All we want is for the Iranian authorities and leaders to find it in their hearts to extend the same compassion that they did to me to Shane and Josh,'' she said.