Iran had sought to deter Donald Trump from joining Israel’s bombing campaign with dire threats of retaliation, but its options now are limited and fraught with risk.

Iranian officials have said specifically that US ships and military bases would be targeted, but much of the capacity it had relied on as a deterrent has been stripped away over the past few days by Israeli strikes. Those strikes however, have focused on long-range ballistic missile launchers. Iran still has a formidable arsenal of shorter-range missiles and drones.

The US has taken precautions over the past few weeks, dispersing its naval presence in the region and beefing up air defences, to try to ensure it presents as hard a target as possible.

Furthermore, Trump warned of broader US involvement in Israel’s war if Iran attempts to strike back, and in recent days suggested that one of the targets for US bombers would be the supreme leader, Ayatollah Ali Khamenei.

3:01 Iran must make peace or ‘future attacks will be far greater’, Trump says in address – video

Iran’s other principal weapon, built up over decades, is its network of alliances with regional militias, its “axis of resistance” but that too has been depleted. Hezbollah’s extensive missile arsenal was pulverised by the Israeli air force last year. Israeli planes have returned to keep the Lebanese Shia force in check, bombing an alleged missile stockpile in south Beirut in April.

A Tehran-backed Shia militia in Iraq, Kata’ib Hezbollah, has threatened to target “US interests” in the Middle East in response to Washington’s participation in Israel’s support. One of its commanders, Abu Ali al-Askari, was quoted on CNN as saying that US bases in the region “will become akin to duck-hunting grounds”. The United States has military facilities across at least nineteen sites across the Middle East, eight of them permanent.

Another Iranian partner, the Houthi forces in Yemen, agreed a ceasefire with the US in May but they have warned they would regard the truce to be broken if Trump decided to take part in attacks on Iran, and would target US ships in the Red Sea, something the Houthis have done with mixed results in the past.

The entry of any of these militias into the war would draw a devastating response from the US, which has been preparing for just such a contingency over the months that Israel has been preparing its attack.

Iran also has the option of attacking shipping, with the ultimate option of using mines, sinking vessels or issuing credible threats to close the strait of Hormuz, a narrow gateway to the Persian Gulf just 55 km wide in some places, through which over a fifth of the world’s oil supply, 20m barrels, and much of its liquified gas, passes each day.

Hardline Iranian politicians have called for the strait to be closed over the past few days. It has the advantage of being a means to impose a direct cost on Trump, as it would trigger an oil price spike with a near immediate inflationary effect in the US ahead of congressional elections next year. But it would also be an act of dramatic economic self-harm. Iranian oil uses the same gateway, and shutting Hormuz risks bringing Gulf Arab states, who have been highly critical of the Israeli attack, into the war to safeguard their own interests.

To avoid bringing further adversaries into the conflict or inviting an all-out US bombing campaign, Tehran could decide to serve its revenge cold, at some later date. In the past, it has delayed its response to attacks from outside. The foreign minister, Seyed Abbas Araghchi, hinted at such open-ended retaliation when he said on Sunday that Trump’s decision “will have everlasting consequences”.