The MX blockbuster missile is in trouble because of political resistance in the West where it would be deployed and doubts about whether it makes sense to build the weapon at all in the absence of an arms control agreement.

Republican Sen. Jake Garn of Utah, an early enthusiast of the MX, which would go in his state, warned yesterday the public opinion out West is souring on the missile and that the Pentagon had better consider a different deployment scheme.

The General Accounting Office, meanwhile, is predicting the MX will cost almost twice the $33 billion expected price tag and could be neutralized by unrestricted production of Soviet warheads.

The attitude toward the nuclear missile is so "incredibly adverse," Garn told Defense Secretary Harold Brown, "that you've got to honestly look at alternatives" to the current deployment plan.

Garn said that neither his state nor neighboring Nevada could handle the army of workers, and their families, to build this biggest of all missile projects.

"Public opinion has really turned," Garn said at a Senate Appropriations Committee hearing on the Pentagon's budget. "You have serious problems in my state and Nevada. You have problems with me. And you could never accuse me of being anti-defense."

Garn urged Brown and his fellow witness, Gen. David C. Jones, chairman of the Joint Chiefs of Staff, to find an alternative to the "racetrack" pattern of deployment envisioned for the MX -- including spreading it over more states.

Under the current deployment scheme, each of 200 MX missiles would be hauled secretly from one concrete garage to another arranged around a dirt-road "racetrack." The idea is to keep Soviet gunners guessing about which of the 23 identical garages, spread a mile apart, holds the missile at each of the 200 "racetracks."

The Air Force plans to use 10,000 square miles of land on the valley floors of Nevada and Utah for these MX racetracks. Air Force assurances that only 25 square miles would be fenced off from ranchers and others have failed so far to allay public fears about losing the entire 10,000 square miles to the military.

To build the MX, the Air Force estimates that 100,000 people -- 25,000 workers and 75,000 dependents -- would have to move to Nevada and Utah. This prospect, Garn said, has put mayors and other politicians at battle stations as they worry about their schools and water supplies being over-whelmed.

"These are mayors who work for $50 a month," Garn said. "You don't find people any more patriotic. They are incredibly concerned."

Replied Brown, in a reference to the racetrack scheme: "We have to begin with the system we believe to be the most cost-effective. We may be able to make some modifications even if it erodes" the cost-effectiveness of that deployment.

Garn said that he and fellow Republican Paul Laxalt of Nevada will conduct hearings this spring to assess the MX impact on their states.

Garn's warning that public opinion is running against MX comes as a congressional watchdog agency, the General Accounting Office, is challenging the project.

GAO, in a Feb. 29 report entitled "The MX Weapon System -- A Program with Cost and Schedule Uncertainties," predicted that inflation will increase the projects cost to "at least $56 billion." The Pentagon has been predicting a cost of $33 billion in fiscal 1980 dollars. Neither estimate includes the cost of the nuclear warheads for the MX.

"The high cost of the MX system raises a serious question regarding its affordability," given Pentagon budget limitations, GAO said.

The agency said "the Air Force has yet to conclusively demonstrate" that there would be enough electricity, water and building materials to construct the MX system. The Air Force hopes to have the first missiles ready for duty by July 1986.

Also, with the derailment of the strategic arms limitation treaty (SALT II), the Soviet Union "could build enough weapons to neutralize the MX," GAO said.

If the Soviets should build enough warheads to cover all 4,600 shelters for hiding the MX, Air Force officers have said, the United States could construct more shelters. It would be more expensive for the Soviets to build warheads than for the United States to construct additional shelters, according to the Air Force.

GAO recommended that Brown report on what changes the lack on an arms control agreement would force upon the MX.

An Air Force spokesman said yesterday that most of the problems spotlighted by GAO are those "normally resolved" in the current full-scale development phase of the MX.