U.S. Marines at "the tip of the spear" defending Saudi oilfields were told by their boss Wednesday to expect a long desert stay.

"I don't want to hear about any more questions about how long you're going to be here," Commandant Gen. Alfred Gray told Marines at a combat support camp in the northern Saudi desert near the main highways to the country's major oil installations.He also said the Marines should be prepared to shift to offense if the kingdom is attacked.

Gray, speaking to reporters after his 45-minute pep talk, said he was confident the multinational force in Saudi Arabia and the gulf region could stop any Iraqi offensive. But he refused to say whether the U.S.-led forces were capable of pushing Iraq out of Kuwait.

During his speech to the men, Gray said, "We have a very, very powerful, flexible and most useful force, afloat and ashore, ready to do whatever needs to be done. We're going to play for keeps if that is required."

For now, he said, the mission was defensive and 13 ships were headed to the region with supplies needed to sustain the Marine force.

But should hostilities break out, Gray said, "We all know the best defense is a good offense."

Gray's pep talk, delivered through a bullhorn, was full of praise for the Marines but equally rich with reminders that their stay in the desert is unlikely to end soon.

"How long are we going to be here?" he asked rhetorically. "Well, we're going to be here until we get done what has to be done."

He then essentially ordered the troops not to complain.

"There will be no morale problem . . . because I say there will be morale. There will also be no boredom."

Gray said that under normal circumstances Marines are deployed for six months and then brought home for 15 to 18 months.

"It would make sense if we could hold to that as best we can," Gray told reporters. "But we may not be able to because we have, as I tried to indicate, enormous global commitments. I think they understand that."

Gray reminded the Marines to be on guard against possible terrorist attacks, saying, "Marines are always the No. 1 target in this part of the world for terrorist attack."

"You're the tip of the spear," he said.