A mood of confrontation in the Gulf has been steadily increasing since Sunday, when the USS Nimitz with 80 warplanes aboard, arrived just 24 hours after Iran had begun its annual manoeuvres, code-named Pirouzi (Victory).
In response, Tehran declared it would "react decisively" to any aggressive action by the US fleet, and yesterday denounced both Britain and America for spying on its war games, during which it claims to have tested successfully a new unpiloted stealth aircraft. Singled out for special mention was the British destroyer Nottingham, accused of sailing "within shooting distance" of Iranian warships, before heeding a warning to move away at once.
In London and Washington, officials were playing down the affair.The Ministry of Defence last night did confirm the Nottingham had been "in the vicinity" of Iranian vessels on Tuesday, but outside the 12-mile territorial limit. "We believe no incident took place," a spokesman said, and Pentagon officials were similarly dismissive.
In fact, the current concern of the Allies is not so much the ultimate nightmare of a move by Tehran to close the Straits of Hormuz and thus choke off the West's vital oil pipeline, as fresh defiance from Saddam Hussein. Once again, the Iraqi dictator is out to exploit any pretexts to break the strategic strait-jacket of the two no-fly-zones that effectively confine his airforce to the middle third of his country.
On 29 September came the latest opportunity: cross-border attacks by Iranian government planes against bases of the Iranian Mujahedin opposition, which is actively supported by Baghdad. In response to this violation of the southern no-fly-zone, Saddam committed one of his own by scrambling Iraqi fighters to chase off the intruders.
But, British officials noted last night, this was just one of a string of recent infringements - others apparently some 400 miles to the north, where Kurdish factions are battling for control of Kurdish regions of Iraq. Though Turkey yesterday denied any involvement, the Patriotic Union of Kurdistan accused Ankara of twice bombing PUK-controlled territory, in support of the rival Kurdistan Democratic Party.
The hostilities signalled the end of a UN-brokered ceasefire that had held for the previous 12 months, designed in part to prevent Saddam exploiting differences between the factions to reassert his influence in the Kurdish segment of his country.
Almost certainly the despatch of the Nimitz - which has not been accused by Iran of snooping on its exercises - is designed to send a clear message to Saddam to toe the line. "If these violations continue, he should be aware the coalition will strike back," a Western diplomat said last night.
No less significantly, the Iraqi provocations come at a well tried moment. As he has done in the past, Saddam may be trying to deflect attention from the latest report of the UN special commission that theoretically enforces the destruction by Iraq of its chemical and biological weapons, and equipment that could be used to build nuclear bombs. Once again, Baghdad is not complying, meaning that UN sanctions against Iraq will continue.
If he stays true to form, Saddam will back down rather than invite an allied reprisal. But in a region that is always unpredictable, the Iranian dimension adds a further risk.
Despite some signs that Washington is seeking to improve relations with the new - and conceivably more conciliatory - government in Tehran, Iran is still deemed a "rogue state" and US policy remains the "dual containment" of both Iraq and Iran. Nor does fierce criticism of the recent Franco- Russian gas deal with Iran suggest any softening of the Clinton administration's stance.
The proximity of US warships and Iranian planes in the Gulf can prove a volatile and tragic combination, as on July 1988 when the US cruiser Vincennes mistakenly shot down an Iranian civilian jet, killing all 290 people aboard. Five months later, possibly in reprisal, came the bombing of PanAm flight 103 over Lockerbie.