U.S. By Jana ChoukeirDUBAI, Sept 20 (Reuters) - Iran warned on Sunday against any big new attack by the United States and its allies, saying it had information such a move was being prepared, adding to the anxiety in a region already on edge after drone and missile strikes on Saudi Arabia. Key points and original sources are listed below.

• U.S. State Department issues security alert highlighting potential for escalation in Middle EastS1

• By Jana ChoukeirDUBAI, Sept 20 (Reuters) - Iran warned on Sunday against any big new attack by the United States and its allies, saying it had information such a move was being prepared, adding to the anxiety in a region already on edge after drone and missile...S2