Secretary of Defense Caspar W. Weinberger and Republican Sens. Paul Laxalt of Nevada and Jake Garn of Utah all described yesterday as inaccurate widespread newspaper and television news reports that President Reagan had decided to deploy 100 MX missiles in 1,000 protective silos in specific locations in the western United States.

The president is scheduled to announce Friday his decisions on the MX and on a new bomber for the Air Force. Weinberger said yesterday on the ABC-TV show "Good Morning America" that "if people would only wait until the president has made his decision and made his announcement we'd all get it accurate."

A number of well-placed officials in the Pentagon, Air Force, White House and on Capitol Hill estimated that perhaps only a half dozen people, including the president, knew what would be announced, and that below that level there was considerable agitation and confusion. One informant said that Pentagon officials had just been told to prepare briefing material for several alternative decisions, suggesting that it may well be that a final choice still has not been made.

Sources generally expressed confidence that 100 missiles would be built but some suggested that the final plan might involve a combination of fewer new shelters in the West with other MX missiles put on existing Minuteman missile bases.

On Tuesday night, all three major television networks broadcast reports that Reagan had decided on the 100 missile-1,000 silo plan, although the accounts differed somewhat on where the silos would be based. Most reports focused on Nevada, while some mentioned Utah and the Dakotas as well. Wednesday morning, a front-page Washington Post story also reported a decision to base the missiles in Nevada, but noted that some senior administration officials were cautioning that the 100 missile-1,000 shelter plan in Nevada was "not totally correct."

Roughly similar accounts reporting a decision to deploy the 100-1,000 combination in the West, and attributed to congressional and administration sources, also appeared in The Wall Street Journal and in the later editions of The New York Times yesterday.

Asked about this on the TV program, Weinberger, who has frequently criticized reporting throughout the drawn-out MX decision-making process, said that "it's an awesome responsibility to take on The Washington Post and all the networks, but the simple fact of the matter is that I have never in my experience, short as it has been, seen so many errors about so many different parts of a single story."

Garn, who attended a regular Republican leadership meeting at the White House yesterday, had a few moments alone with the president and said Reagan "confirmed that the reports about the MX missile deployment decision on CBS and the other major news media were absolutely wrong. Although I still don't know what his decision will be, the reports that the president would be placing 100 MX missiles in 1,000 silos in Utah and Nevada are not true, and that came right from the top."

Garn's statement seemed to leave open the idea of a Nevada deployment. But Laxalt seemed to rule that out, at least regarding 1,000 shelters. Laxalt also attended the White House meeting and said later, "I have been assured by the White House that reports that 100 missiles will be lcoated in 1,000 silos in southern Nevada are not true." If "confusion reigns," Laxalt added, the president will clear it up Friday.

Nevertheless, reports persisted yesterday, despite the disclaimers. United Press International quoted a White House source as saying the press accounts were "fairly well on target" and the Associated Press, quoting a "knowledgeable Senate source," reported that the decision was the 100 missile-1,000 silo plan for the western U.S. but suggested Reagan had not yet decided exactly where to place the missiles.

Normally well-informed sources within the administration held out the following possibilites.

The president could decide to go ahead with something less than 1,000 shelters, putting some on military bases such as Nellis Air Force Base in Nevada and putting other missiles into existing Minuteman silos in other states or perhaps into new, vertical shelters on other Minuteman bases in Montana and Wyoming.

Last June, Laxalt and Garn proposed putting all the MX missiles into existing Minuteman silos at the Grand Forks base in North Dakota, where they could be protected by a small force of 100 defensive anti-ballistic missiles allowed by the U.S.-Soviet ABM treaty. Some sources said this plan may now be a possibility, although many officials said Congress had ruled it out and virtually no other support existed for such a plan.

The president could also defer a decision on the MX and take time to try to develop a common missile for potential use by both the Air Force and Navy.

Sen. Robert J. Dole (R-Kan.) said that "low-level" officials at one point had approached him to ask if it would be acceptable to put MX missiles in existing Titan missile silos that are scheduled to be vacated in his state.