Foreign ministers from the major powers have agreed to refer Iran back to the UN Security Council for possible punishment over its nuclear programme.
The decision by the Security Council's five permanent members plus Germany could lead to economic sanctions.
Ministers meeting in Paris said Tehran has not signalled it was seriously considering incentives designed to get it to abandon uranium enrichment.
But any threats of punishment by the UN would not include military force.
Uranium enrichment produces fuel for power plants or weapons.