A top adviser of Iran's supreme leader has warned that in the event of war all ships passing through the oil-rich Gulf region would be within the reach of Iran's missiles, a government newspaper reported yesterday.

Iran, embroiled in a stand-off with the West over its nuclear ambitions, has said it could respond to any military attack by closing the strait at the southern end of the Gulf through which about 40 per cent of the world's traded oil passes.

The US, whose naval Fifth Fleet is based in the Gulf state of Bahrain, has vowed to keep shipping lanes opened.

The West accuses Tehran of seeking to build nuclear warheads but Iran, the world's fourth largest oil producer, says its aim is to master technology to make electricity. Washington has not ruled out military action if diplomacy fails to end the row.

"At a time of war no ship can pass through the region of the Persian Gulf without being in the reach of the Revolutionary Guards' coast-to-sea missiles," Yahya Rahim-Safavi, a senior military adviser of Supreme Leader Ayatollah Ali Khamenei, was quoted by the Iran daily as saying.

He said earlier this week that Ayatollah Khamenei had put the elite Guards in charge of defending the Gulf against any attacks and that they would not hesitate to "confront foreign forces".

The comments came amid persistent speculation about a possible US or Israeli strike on Iran's nuclear facilities.