Washington: A US missile struck a small Iranian oil tanker near Kharg Island on Saturday, according to Iranian media, as tensions between Washington and Tehran remain high following months of conflict. Iran’s Student News Agency reported that no casualties were recorded in the incident.

Kharg Island is a key part of Iran’s oil export infrastructure and handles an estimated 90 to 95 per cent of the country’s crude exports. US President Donald Trump had previously threatened to take control of the island.

Regional tensions have escalated since US and Israeli attacks on Iran began on February 28. Tehran has responded with missile and drone strikes against Israel and US interests across the region.

Washington and Tehran signed a memorandum of understanding on June 18 concerning freedom of navigation through the Strait of Hormuz. However, implementation has stalled amid disagreements over security arrangements in the strategic waterway.

Separately, US military investigators administered polygraph tests in August to about 50 military officers and civilian officials as part of an investigation into leaks involving American munitions stocks, according to media reports.

The New York Times reported that the inquiry focused on personnel linked to the Joint Staff, which advises the president on military matters. Investigators were examining disclosures about shortages of long-range missiles and Patriot interceptors during the war with Iran.

CBS News reported that the FBI was not involved in the polygraph examinations and that the military conducted the investigation internally. Not all senior leaders were tested, with Chairman of the Joint Chiefs of Staff General Dan Caine reportedly excluded.

No officials failed the questions intended to determine whether they had leaked information to the media, CBS reported. Investigators were also examining whether a government official could have been acting as a foreign spy because access to the munitions information was tightly restricted.

Pentagon spokesman Sean Parnell said the department did not comment on internal personnel or investigative matters but took classified leaks seriously.

Trump has denied reports of strategic weapons shortages, saying the US military has “massive amounts” of weaponry. He described the disclosures as treasonous statements and fake news and warned that those responsible would face severe prison sentences.

The investigation followed other unauthorised disclosures, including part of the Secretary of Defence Orders Book. The document reportedly showed six four-star leaders opposing an extension of large-scale operations against Iran, saying the war was unsustainable and was reducing global military readiness.

Meanwhile, US Congressman Ted Lieu has questioned the Trump administration’s description of Iran as a “failed state”, citing Tehran’s continued ability to launch missiles and drones against US bases and allies.

Lieu also questioned the impact of the conflict on Americans, including the reported average US petrol price of $4.12 a gallon. He called for greater transparency over the war and asked how the US would eventually end the conflict.

Axios separately reported that the Trump administration was drafting a post-war plan for the Middle East. The plan remains at an early stage and is intended to guide US policy in the region after the Iran war ends.