Is it too late to oppose the war, or too soon? People argue as they watch their screens. The first major national peace demonstration is due to be unfurled on Saturday. By all accounts, it will be large but not star-studded.

No Congress people will be on the platform. Even those most fiercely opposed to the use of force in the recent debate apparently will hold their fire until the ground war begins and the "human remains pouches," which were formerly called body bags, come back. Three well-worn figures head the speakers list: D.C. "shadow senator" Jesse Jackson, Molly Yard of the National Organization for Women, and professional dissenter Daniel Ellsberg. The stars who brought the crowds in the Vietnam years are also hanging back, wondering if it is wise, career-wise, to step out against a war that has scarcely begun -- and in its first week displayed not a single corpse.

The principal organizer, the National Campaign for Peace in the Middle East, has programmed the event to begin at noon at the Capitol and end at the Ellipse. They are getting much flak and being importuned to "support our fighting men and women." They receive strong hints that it is not patriotic to exercise free speech while 500,000 Americans are in peril in an attempt to restore the feudal monarchy of Kuwait. The dispute about who cares more about our brave fighting men, the government that sends them into battle or dissidents who try to stop the war and bring them home, is left over from Vietnam and will not be resolved this weekend.

"It's not the time," the organizers are told. One of the coordinators, Bonnie Garvin, is having trouble with her parents, old-line liberals who brought her up on leftist causes, now turned off. The plight of Israel, of fellow Jews being slammed by Scud missiles, has destroyed their enthusiasm for the march. They will not attend.

Old peaceniks in the West complain that enormous crowds are turned out, as in San Francisco, but that the demonstrations fall into the hands of special pleaders, advocates who simply use the occasion to plead for gay and lesbian rights.

But traditionally anti-war gatherings have had the same old speakers. It is the infantry, not the air, which matters at these affairs. The audience rarely listens too closely to what is said; they draw sustenance from each other and the body count. The numbers are always contested, and produce enormous paranoia in the marchers, who believe the police diminish them to please the authorities.

Sen. John McCain (R-Ariz.), a Vietnam War pilot shot down and held captive for five years, played host on an Arizona talk-show. Many callers raged against the protest, demanded it be stopped. But one woman raged at McCain's vote for the war. She had been watching the wretched American POWs on television: "How could you vote to send anyone into a situation like that?"

The Israelis take the position that if their pilots are paraded on television, they should smile and rob the sight of all its propaganda value. Since Vietnam, during which our POWs were adjured to give only name, rank, serial number and date of birth, we have modified the policy to the point where we just require them to do the best they can under mistreatment and torture. But the feeling that they should hold out lingers, and we cannot seem to emulate the wise Israeli attitude that those who see the pilots damning their country should be glad the pilots are alive.

Men, primarily, take the position that, since the war has started, nothing can be done or should be done to try to stop it. Women often feel otherwise. One who does is Peg Mullen, a Vietnam Gold Star mother, who is bringing a busload of fellow citizens from Brownsville, Tex., to the demonstration.

She wondered about it for some time. Her oldest son, Michael, was killed in Vietnam in 1970, by friendly fire. A book by that name was written about her long bitter efforts to find out what happened to her son.

Peg Mullen, who lived most of her life in Iowa, is the reason Sen. Charles E. Grassley voted against the war. He was one of few Republicans to do so, and he told the Des Moines Register that he was "influenced by a woman who lost a son in the war." He declined to go to war for "minerals, macho and monarchy."

She wondered about coming, wondered what good it would do. She is 74, and the bus trip takes 37 hours, but she decided she had to come. She thinks that demonstrations may do more for the participants than for presidents. "It's a way of venting anger," she says.

An official of the Johnson administration, who does not wish to make public comment about the war at this time, said, "Demonstrations are of value. They display opposition to a war they believe is unworthy."