Naval Blockade Option Is Readied : Sanctions: The move would involve halting cargoes at the ports of three nations. Planners say it’s a most difficult exercise.

WASHINGTON â€”  The Pentagon’s war planners Monday offered the White House the option of an unprecedented allied naval blockade of Iraq’s oil trade if necessary to enforce sanctions voted by the United Nations.

But even as the United States and allied navies drafted plans for such an operation, they said their recent experience in the Persian Gulf has not prepared them well for this more difficult task. Stopping cargoes from a nation whose exports leave through three ports in three different nations is trickier, they said, than escorting ships through a single channel in wartime.

“Denying freedom on the high seas is a business we haven’t been in for a long time,� one knowledgeable naval officer said. “I don’t think there’s anyone around here that knows exactly how to plan it.�

As they consider a blockade--in international law an act of war--naval officers pointed out it would require a large numbers of warships in the Red Sea, the Mediterranean and the gulf.

Pentagon officials have told the President that the operation would be too large for the U.S. Navy to enforce alone. That fact, sources said, underlined the importance of President Bush’s meeting Monday with NATO Secretary General Manfred Woerner and with British Prime Minister Margaret Thatcher, whose naval forces have cooperated with the U.S. Navy before in the gulf.

Unless allied navies would join in the effort, a blockade would likely be too costly and difficult to conduct effectively.

Pentagon officials said Monday that a blockade is just one of many military options the United States is considering to bring Iraqi President Saddam Hussein to his knees. Meanwhile, American warplanes available from bases throughout Western Europe and the southeastern United States are “spring-loaded� for deployment to Saudi Arabia.

Whether they go will depend on the outcome of meetings that took place Monday between U.S. Defense Secretary Dick Cheney and Saudi Arabia’s King Fahd. Cheney left Sunday night for Riyadh, where American officials said he would press the Saudis to take action against Iraq and to allow U.S. forces access to Saudi bases to lead the effort.

The officials said Cheney was expected to press the Saudi leader for a rapid decision, because it could take days or weeks for U.S. forces to arrive in numbers and with equipment sufficient to fight.

“If Saudi Arabia waits until the 11th hour, it may be too late,� said one Administration official. “Among the things Cheney is explaining is what that means. Fahd and Saudi Arabian civilians have to know how much the United States will do, what it will take from them and what (timetables are required for making the decision).

“Implicitly, when you explain the time lines, you tell them, ‘If you call too late, you can’t expect us to get there,’ � the official added.

By attempting to deny the passage of Iraqi oil from those three ports, naval forces could face some of the same problems that bedevilled navies during in the much-simpler Persian Gulf escort operation. Iraq could seed the gulf with mines. U.S. carriers cannot operate within the constrained waters of the gulf, and thus aircraft intended to protect navy ships against attacking Iraqi warplanes are operating at the outer limits of their range.

And Iran and Iraq’s Chinese-made Silkworm missiles, possibly tipped with chemical weapons, would cast a long and dangerous shadow over the navy forces operating inside the gulf.

If the United States and its allies act together to blockade Iraqi oil, they would dispatch dozens of warships, mainly cruisers and guided missile destroyers, to patrol the narrow bodies of water of the gulf, the Red Sea and the northwest corner of the Mediterranean. There--at the ports of Yumurtalik, Turkey, Yanbu, on the Red Sea coast of Saudi Arabia, and Jubayl in Lebanon north of Beirut--oil is loaded onto ships from pipelines that originate in Iraq.

Those warships would stop, search and detain any ships carrying Iraqi oil from the ports where it is loaded onto tankers from Iraqi pipelines. Depending on how far the allied effort would go, the blockade also would likely choke off the supply of imports--including food--into Iraq.

The Red Sea and the gulf are both long channels of water with narrow exit and entry points which could be used as a gateway for checking traffic in and out, officials said. But military officials said you could not rely entirely on the gateway to catch all ships, and thus the navy would also patrol large areas along the length of those waters, stopping ships suspected of carrying “contraband.�

In all three areas, the volume of ship traffic that could be stopped could be substantial.