TEHRAN, Iran - Iran's intelligence minister on Sunday signaled that Tehran might be open to a prisoner swap with the United States for three hikers it has had in jail since July.

The three Americans - Sarah Shourd, 31, of Oakland, Calif.; Shane Bauer, 27, of Pine City, Minn.; and Josh Fattal, 27, whose family lives in Elkins Park - were arrested along the Iraqi border 10 months ago. Iran has accused them of espionage and entering the country illegally; their families say the three were hiking in Iraq's largely peaceful mountainous northern Kurdish region and that if they crossed the border, they did it accidentally.

Last week, Iran allowed the prisoners' mothers to visit them. The women had hoped to secure their release, but they returned Saturday without them.

As a political maneuver, the act was "pretty reminiscent of the Cold War," Temple University law professor Duncan B. Hollis said Sunday night.

"Iran is aware that its image in the West is not all that great," said Hollis, who specializes in international and foreign-affairs law. "Letting the mothers come shows that they're not entirely heartless, and lets Iranian officials claim that they're doing right by the detained folks."

But Iran's posture does not appear to be a level trade for any of about 10 Iranians whom it claims have been unjustly taken into custody by the United States, Hollis said. So long as the United States maintains the hikers were not spies, he said, "I don't see any circumstances in which you're going to be able to manufacture a prisoner swap."

On Sunday, Iranian Intelligence Minister Haidar Moslehi said the three Americans' "status as spies is a clear and obvious case," according to state TV.

But he said there was a chance of discussing a prisoner exchange if Washington made a humanitarian gesture toward Iranians in U.S. custody similar to the one Iran made last week.

Iran has repeatedly accused the United States of abducting about 10 Iranians abroad and sentencing them to prison.

On Thursday, State Department spokesman P.J. Crowley said the U.S. was "not contemplating any kind of a prisoner swap."