The war there is already seen destabilizing neighboring Lebanon, while the body count in Iraq has also been creeping back up as violence between Sunni groups and sometimes Tehran-backed Shi’ites simmers.

The Sunni leadership of almost all of the Gulf states have long suspected Iran of stirring up dissent amongst their Shi’ite populations, although Western diplomats suspect such claims are overstated. Some worry Washington is already being dragged onto one side in a growing regional blood feud.

Tehran may step up its attempts to destabilize neighbors, particularly if it believes its enemies are trying to do the same. Washington recently removed Iranian militant opposition group MEK from its list of terrorist groups, potentially opening the door to covert co-operation. To work with it on attacks within the country, however, might produce a violent response.

Last year, U.S. officials said they had foiled an Iranian plot to kill the Saudi ambassador to Washington by bombing a restaurant in Washington DC. That, some security experts said, suggested Iran was increasingly willing to take serious risks -- although others said the entire tale sounded too far-fetched.

“It’s very easy to look at these events and tie them together in some kind of straightforward narrative,” says Henry Smith, Middle East analyst for London-based consultancy Control Risks. “But in reality, things are likely to be far more complex.”