Iran denied on April 3 that US forces had carried out a helicopter-borne assault on Kharg Island, the country's main crude oil export hub in the Persian Gulf, Tasnim News Agency reported from the island.

Tasnim's correspondent on Kharg said the reports circulating on social media were false and that "complete security" prevailed on the island.

The armed forces had "full control" of the situation and all areas were under continuous surveillance, the report said.

The denial came as speculation intensified over a possible US ground operation targeting Iranian coastal and island infrastructure. US media reported on March 29 that the Pentagon had drawn up plans for weeks of limited ground operations including raids on Kharg Island and sites near the Strait of Hormuz.

Trump told the Financial Times on March 30 that "maybe we take Kharg Island, maybe we don't. We have a lot of options." He said any operation would require a sustained US presence on the island.

Kharg Island handles roughly 90% of Iran's crude oil exports and has been a central point of discussion in US war planning. The island sits in the northern Persian Gulf and would be a high-value target for any operation aimed at seizing Iranian energy infrastructure.

Iran's armed forces spokesman said on April 2 that Tehran was waiting for a US ground invasion and would turn it into "a slaughterhouse." Parliament Speaker Mohammad Bagher Ghalibaf claimed 7mn Iranians had volunteered in under a week to defend the country against a land assault.

White House press secretary Karoline Leavitt said Pentagon preparations were intended to give the president "maximum optionality" and did not indicate a final decision had been taken.