A scrubby island in the Gulf that is roughly one third the size of Manhattan, Kharg Island is the nerve centre of the Iranian oil industry — and at the heart of US President Donald Trump’s latest efforts to pressure Tehran.

On Monday, Trump vowed that a failure by Iran to agree a deal to end the war could see the United States “completely obliterating” the export hub.

A day earlier, he had said the United States could take the island, eyed by the Pentagon for ground operations, “very easily”.

So what are Trump’s options, and how might Iran react if he presses on this pressure point?

What is Kharg Island?

It may be a mere scrap of land, but Kharg handles around 90 per cent of Iran’s crude exports, according to a report by US bank JP Morgan.

Located in the north of the Gulf, around 30 kilometres from the Iranian coast and more than 500km from the Strait of Hormuz, it has no oil wells.

But it has Iran’s largest oil terminal, oil pipelines, storage tanks and related infrastructure.

It also has military facilities, some of which have already been hit by Israeli-US strikes.

On March 13, “US forces executed a large-scale precision strike on Kharg Island”, Centcom, the US military command for the region, said.

“The strike destroyed naval mine storage facilities, missile storage bunkers and multiple other military sites. US forces successfully struck more than 90 Iranian military targets on Kharg Island, while preserving the oil infrastructure.”

Sources close to US intelligence services told US broadcaster CNN Iran had deployed additional troops and defence systems to the area in recent weeks, including MANPAD-type surface-to-air missiles and mines.

Trump’s options?

There appear to be three routes for US forces wishing to seize the island — an airborne attack; an amphibious operation; or a combination of the two.

The Pentagon is currently moving US paratroopers and Marines into the area.

“(The) US combat force build-up sets the stage for (a) potential ground offensive in Iran,” said US think tank Soufan.

Centcom former commander General Joseph Votel told The War Zone website this month that it would not take that many soldiers to seize Kharg.

“On a small island like Kharg, I imagine you’d need a battalion of Marines. We are therefore talking about a force of 800 to 1,000 men, perhaps a little fewer, certainly not much more,” he said.

But taking Kharg and holding onto it “are two different things”, stressed Professor Phillips O’Brien of the University of St Andrews in Scotland.

He said the US military would struggle to retain the island within range of Iranian missiles and drones.

Just 60km away is the city of Bushehr, an important military centre “from which the Iranians defend the entire northern part of the Gulf, including Kharg”, noted Pierre Razoux of French research centre FMES.

Why do it?

Trump’s war goals remain hazy. It is unclear whether he primarily wants to force Iran to reopen shipping lanes in the Strait of Hormuz; force regime change in Tehran; coerce the Iranians into concessions on their nuclear or ballistic missile programmes.

In the short term, capturing Kharg could give Washington leverage to force Iran to negotiate — presumably on Trump’s terms, given the country’s dependence on oil revenue, the Soufan Center said.

It might not have much effect in reopening the Gulf to shipping, however, because Iran controls a string of other islands in the Strait of Hormuz.

And if the Iranians choose not to cede to Trump’s demands, “What does the US do?”, O’Brien wondered.

“Does the US then, out of spite, level all the economic facilities on Kharg?

“That could easily boomerang back in American faces. It means oil prices skyrocket even more and stay high for much longer,” he said.

“It also means Iran will be incentivised to shut down the traffic in the Straits for even longer. If they cannot get their own oil out, why let anyone else’s?”