TEHERAN: Iran accused three detained Americans of spying on Monday, signaling Teheran intends to put them on trial. It drew a sharp US response that the charges are baseless because the hikers strayed across the border from Iraq.

The announcement comes as Washington and Teheran are deadlocked in negotiations over Iran's nuclear program, raising concern that the three could be used as bargaining chips in the talks or to seek the return of Iranians they say are missing.

Relatives and the US government say the three were innocent tourists on an adventure hike in northern Iraq and accidentally crossed into Iran where they were arrested on July 31.