The US has informed several Gulf nations it may launch a “brief but intense” military operation against Iran after the midterm elections on November 3, the Wall Street Journal reported on Wednesday.

According to the newspaper the warnings were passed on through diplomatic and military channels.

Its sources said Washington and Israel are preparing for a fresh wave of attacks intended to weaken Iran and pressure it back to negotiations.

President Donald Trump has not made a final decision, though the Journal reported that he is seriously considering extensive operations after the elections, with Iranian infrastructure and nuclear facilities among the possible targets.

The US military is reportedly moving an additional Patriot missile defence system from Texas to Israel to help counter any Iranian retaliation.

The newspaper said the movement was identified from flight tracking data and confirmed by two officials familiar with the weaponry.

US personnel are also being withdrawn from bases in the Middle East considered vulnerable to Iranian attack.

Ammunition stocks are being built up, and plans are being made for the possible use of fighter and bomber aircraft.

There are already 20 warships near the Persian Gulf, and an additional aircraft carrier strike group and a Marine expeditionary unit are expected to arrive.

The war is in its eighth month, and by mid-October its cost was estimated at $47.1 billion, a figure that does not include damage to US military installations in the Middle East.

About $29 billion of the total, almost 60 per cent, has gone on munitions, including Tomahawk and Patriot missiles.