The United States has carried out strikes on two Iranian rocket launchers on Larak Island in the Strait of Hormuz, marking its first direct attacks on Iran since late July.

A US Central Command spokesman, Navy Capt. Tim Hawkins, said the Iranian Revolutionary Guards had been observed preparing to launch rockets carrying sea mines into the strategic waterway.

He said the US military carried out the strikes to prevent the planned operation and protect the free flow of commercial shipping through the Strait of Hormuz.

The strikes came as the US-Iran conflict reached its six-month mark, following a period in which Washington had largely shifted its focus from military action to economic pressure against Tehran.

The Strait of Hormuz has remained heavily restricted since the conflict began, affecting a major global energy route through which about one-fifth of the world's oil previously passed.

Hawkins said US forces had completed clearing sea mines from international shipping routes through the strait and remained prepared to protect the waterway.

Iran has effectively blocked the strait amid the conflict, while diplomatic efforts led by countries including Pakistan and Qatar have so far failed to secure a lasting peace agreement.

A ceasefire reached in April brought an end to the most intense fighting, while a memorandum of understanding towards a final peace agreement was signed in June.

However, sporadic attacks around the Strait of Hormuz have continued to undermine efforts to end the conflict.

The United States has also imposed increasing economic pressure on Iran, including a naval counterblockade of Iranian ports that has contributed to shortages of petrol supplies.

US Senator Jack Reed, the top Democrat on the Senate Armed Services Committee, criticised President Donald Trump over the conflict, arguing that the administration had yet to achieve its objectives.

Iran's Revolutionary Guards subsequently said the US strikes caused casualties and reported retaliatory attacks against US military targets in Jordan.