It wasn't so much what Caspar W. Weinberger said as the way he said it that left the impression he is not a total team player on U.S.-Israeli policy toward Lebanon.

The secretary of defense, speaking at a breakfast meeting with reporters yesterday, characterized in distant terms the startling new idea of sending U.S. Marines to Beirut to do escort service for the exiting Palestine Liberation Organization as "premature discussion of a plan in formation."

Although Weinberger would be in charge of executing the plan, he was noncommittal and vague about its merits and details.

"When you are departing an area, you need something in the nature of a rear guard," he said.

He emphasized that there is "no formal decision or agreement," and something in the tonelessness of his voice suggested that it would be all right with him if there never was.

It is, he said somberly, a risky business. The decision-makers must weigh the difficulties and dangers against "not wanting to be the cause of the thing not working out," he said.

"Not wanting to be the cause of the thing not working out" is as near a formulation of U.S. policy in the present crisis as we are likely to get. From the beginning, the president and his circle have realized that the ferocity of the Israeli action has repelled a number of people, including some of the Israeli participants, and divided the Jewish community.

But the possibility of "cleaning out of the PLO," as Menachem Begin puts it, and simultaneously giving the Soviets a black eye, apparently was irresistible to Weinberger's boss, as it has been to most politicians of both parties in an election year.

The political cost to Reagan seems rather extensive. With his John Wayne reputation, it is extremely dicey for him to send troops anywhere. Having them go to crucified Beirut to bail out the aggressors could be an exceptionally unpopular move.

But the present perceptions are equally dangerous. The president has expressed his determination to be taken seriously as leader of the free world. He insists on "respect" for America. Presently, he looks like Menachem Begin's caddy. Begin wouldn't even let Reagan announce the scheme to send in the Marines--it was leaked on Israeli radio.

Reagan repeatedly issues calls for an end to the violence, for a cease-fire. Yet nightly, apartment buildings are shelled in dying color on home television. He asks for delivery of food and water to the beleaguered city, yet we see vegetable trucks stopped at the barricades, and Wednesday's haunting photograph of a little girl at an empty water faucet.

He has announced $50 million in aid to Lebanon. But the stories from the front say the International Red Cross is not allowed in to provide relief.

Weinberger, the big nuclear hawk in the administration, has been the most outspoken Cabinet critic of the Israeli invasion. He is a confrontationalist with regard to the Soviets, and that was said to be the source of his feud with Alexander Haig.

But he is, unlike Reagan, unmoved by the East-West aspects of the Beirut situation. Haig was tagged as the architect of the unconditional support for Israel. But since his departure, Reagan has continued the acquiescent rhetoric about America's fractious, rampaging client in Jerusalem.

Weinberger again expressed his doubt yesterday that "there is ever a situation where a unilateral resort to force advances the interests of the U.S. or its allies."

He would not say whether anyone in the White House had suggested the simple expedient of cutting off arms shipments when Israel went beyond its original, stated destination in Lebanon.

What we need in the Middle East, he said, are "a number of friends."

He did not volunteer to explain how the advent of the Marines would widen our circle in the Arab world. He was vague when asked how many troops would be needed to protect the Marines who will be protecting PLO guerrillas as they head for the ships, and presumably oblivion.

The diplomatic complexities are baffling. Seeking the agreement of the PLO seems to be de facto recognition. If Philip Habib could get representatives of the PLO at a table with the Lebanese and the Israelis, they might get the hang of talking to one another and perhaps work out something that would not require the leathernecks.

Weinberger seems far more aware than his old friend in the White House of political dangers involved in U.S. failure to exert control, or even influence, on a small state that depends on us for existence.

We were not consulted when the Israelis invaded Lebanon. We were not consulted when they "went on to other objectives."

Why weren't we consulted?

"I can't answer that," Weinberger said starkly.

He closed his eyes and seemed to be reading from some TelePrompTer inside his head as he mentioned, without any expression, our "commitment to Israel's safety and security."

It is obvious that he doesn't think either will be enhanced by dispatching Marines to Beirut.