With the Iraq war over and Afghanistan winding down, worries about the possibility of a new U.S. military conflict focus on Iran.

Despite unprecedented global penalties, Iran's nuclear program is advancing. Western nations fear the Islamic republic is determined to develop nuclear weapons and fundamentally reshape the balance of power in the Middle East. That would pose a grave threat to Israel. Iran says its program is for peaceful energy and research purposes.

Israel could decide to strike Iran's nuclear sites on its own, and Israeli leaders say time to act is running out.

If attacked, Iran might retaliate by disrupting global fuel supplies, striking U.S. personnel and bases in the region or supporting terrorism. The conflict could become a new war in the Muslim world.