The Bush administration began its first offensive military operation against Iraq yesterday when Defense Secretary Richard B. Cheney signed an order to set up what amounts to a blockade of all shipping bound to and from Iraq and occupied Kuwait.

As of last night, no ships carrying affected cargo were near what the administration was calling the "zones of interception."

The order, which was given final approval by President Bush during his visit to the Pentagon Wednesday, sets up interception zones in the Persian Gulf south of Kuwait, in the Gulf of Oman and in the Red Sea approach to Jordan's port at Aqaba.

"The president authorized a multinational maritime effort that will intercept ships carrying the products and commodities that are bound to or from Iraq and Kuwait," a Pentagon statement said.

"All ships we believe to be proceeding to or from Iraq or Kuwait will be intercepted," the statement said, adding, "Vessels bound to or from ports of other countries carrying materials destined for or originating from Iraq or Kuwait will also be intercepted."

A Pentagon official said this latter reference was specifically included to cover Jordan's port of Aqaba, which has served as a transshipment point for Iraqi cargo and which Bush previously said should be cut off as a supply line to the Baghdad regime.

The actual rules sent to U.S. warship commanders were classified and not released by the Pentagon. Spokesman Pete Williams said U.S. commanders will conduct intercepts by "making contact . . . using all available communications," including radio, flags, lights and loudspeakers to determine whether the ship is carrying cargo to Iraq or Kuwait.

If the ship is not bound for the prohibited ports, Williams said it will be allowed to go on its way. "If a ship fails to proceed on its stated or prescribed course . . . it may be stopped and boarded," he said.

"To the maximum extent possible," he said, "we will conduct operations without the use of force. The on-scene commander is, however, authorized to use the minimum force necessary" to ensure compliance with the embargo.

Williams said he would not discuss what a U.S. warship commander would do to a ship that ignores U.S. warnings to heave to for boarding and search. "That is covered by the rules of engagement and we do not discuss that," he said. One military official said that the classified rules do not authorize lethal or disabling fire against any ship and only imply the authority to put a shot across the bow of a ship that resists search or boarding.

Said Williams, "If a ship refuses to be searched or refuses to turn away and if the on-scene commander suspects it is carrying goods" to Iraq or Kuwait, "he may then take the suspect vessel into custody and divert it to a designated port, anchorage or other disposition."

It was unclear what other nations might participate in the interception effort, but Britain and Australia have expressed an interest in using naval action to enforce the U.N. Security Council trade ban against Iraq.

The United Nations itself has not authorized such naval action, but Bush has said that the United States is acting with the authority of the "collective self-defense" provisions of the U.N. Charter and a request by the deposed rulers of Kuwait to block all commerce to Iraq and Kuwait until Iraqi President Saddam Hussein withdraws his occupation forces.