Iran's gunboats stayed out of sight on Saturday as U.S. and allied navies searched Persian Gulf shipping lanes for mines five days after a U.S.-Iranian naval battle, shipping sources said.

"The gunboats are staying in port while American warships patrol the sea-lanes and question merchant ships," one source said. "But no one is relaxing. It could be the calm before the storm."Thirteen mines have been found, five of them on Friday, since the U.S. frigate Samuel B. Roberts hit one on April 14 about 70 miles east of Bahrain.

Iran has denied laying new mines in the Gulf but the blasting of the frigate prompted the United States to destroy two Iranian oil platforms, sparking the clash between the two forces.

Diplomats said Tehran must be wondering what a U.S. review of its navy's "rules of engagement" will produce following clashes last Monday in which Washington said it had sunk or damaged six Iranian vessels.

In Washington, the Pentagon declined comment on a New York Times report that the rules would be revised to allow U.S. Navy ships under unspecified circumstances to protect neutral merchant ships under attack.

Iranian speedboats with makeshift weapons have raided tankers with impunity, generally in retaliation for Iraqi strikes against Iranian oil shipping. U.S. warships have done little more than watch as ships went up in flames and seamen were killed.

Shippers have pressed Western navies to protect all merchant ships, not just their own country's vessels, or those sailing under their flag, as they do now.

While Washington assesses its rules of engagement, Arab countries in the Gulf wonder if Iran's have already changed.

They were shocked by an Iranian attack on Monday on a United Arab Emirates (UAE) offshore oil-field during the height of U.S.-Iranian fighting since the UAE had enjoyed cordial ties with Iran.

The UAE is a major Iranian trading partner and Tehran suggested earlier this year that it might play a mediating role in the Iran-Iraq war, now in its eighth year.

But diplomats said the Iranian attack, followed by a sharp UAE protest to Tehran, soured relations.