The US appears poised to strike Iran within days. While the potential targets are largely predictable, the outcome is not. So, if no last-minute deal can be reached with Tehran and President Donald Trump decides to order US forces to attack, then what are the possible outcomes?

Axar.az reports that BBC Security Correspondent Frank Gardner outlines seven possible scenarios:

1. Targeted, surgical strikes, minimal civilian casualties, a transition to democracy

US air and naval forces conduct limited, precision strikes targeting military bases of Iran's Islamic Revolutionary Guards Corps (IRGC) and the Basij unit - a paramilitary force under the control of the IRGC - ballistic missile launch and storage sites as well as Iran's nuclear programme.

An already weakened regime is toppled, transitioning eventually to a genuine democracy where Iran can rejoin the rest of the world.

2. Regime survives but moderates its policies

This could broadly be called the "Venezuelan model" whereby swift, powerful US action leaves the regime intact but with its policies moderated.

3. Regime collapses, replaced by military rule

Many think this is the most likely possible outcome.

4. Iran retaliates by attacking US forces and neighbours

Iran has vowed to retaliate against any US attack, saying that "its finger is on the trigger".

5. Iran retaliates by laying mines in the Gulf

This has long loomed as a potential threat to global shipping and oil supplies ever since the Iran-Iraq war of 1980-88 when Iran did indeed mine the shipping lanes and Royal Navy minesweepers helped clear them.

6. Iran retaliates, sinking a US warship

A US Navy Captain onboard a warship in the Gulf once told me that one of the threats from Iran he worries about most is a "swarm attack".

This is where Iran launches so many high explosive drones and fast torpedo boats at a single or multiple targets that even the US Navy's formidable close-in defences are unable to eliminate all of them in time.

7. Regime collapses, replaced by chaos

This is a very real danger and is one of the major concerns of neighbours like Qatar and Saudi Arabia.

As well as the possibility of a civil war, such as experienced by Syria, Yemen and Libya, there is also the risk that in the chaos and confusion, ethnic tensions could spill over into armed conflict as Kurds, Baluchis and other minorities look to safeguard their own people amid a nationwide power vacuum.