DHAHRAN, Saudi Arabia — Part of a massive Marine unit deployed off the coast of Saudi Arabia stormed a remote beachhead by sea and air Sunday in a trial run preparing them for a possible amphibious assault against Iraqi forces in Kuwait, according to military sources.

The operation at an undisclosed location used landing craft and more than 90 planes and helicopters to carry hundreds of Marines ashore in a training mission scheduled to last for several more days, the officials said.

A military spokesman here described the landing as a "routine amphibious training exercise," but other officials said it was intended in large part to familiarize shipboard troops with the desert conditions they would encounter in any assault here.

The operation comes amid increasing indications that the Bush Administration is looking with favor on an early-war strategy, including a blunt warning Friday from a top Administration official that Iraq's pillaging of Kuwait had made war more likely.

The landing on foreign soil by the Marine's 4th Expeditionary Brigade is perhaps the boldest in a series of military moves--including the advance of the aircraft carrier Independence to a position inside the Persian Gulf--that appear to send an unambiguous signal about U.S. willingness to use force against Iraq.

Asked whether the training mission was intended to prepare for a possible landing in Iraq or Kuwait, a Marine Corps official here said only, "We do not speculate or comment on future ship or amphibious operations."

Separately Sunday, Prince Sultan ibn Abdulaziz, the Saudi defense minister, told reporters traveling with him in southern Saudi Arabia that "when the doors for peace are closed, the ghosts of war will start appearing."

But Prince Sultan made clear that Saudi Arabia intends to keep its distance from Israel, despite the possibility that country, too, might be drawn into a war against Iraq.

"Israel must stay very far away, totally, from the gulf problem," Sultan said.

"We will not allow Israel--regardless of how severe inter-Arab conflicts are--to defend us against Iraq or against anybody else," he said. "Let it be very well known and very well understood."

The increased attention to the prospect of an amphibious landing by U.S. forces follows sharp increases of Iraqi troop strength apparently designed to counter the threat posed by U.S. ground forces now based in Saudi Arabia.