Major construction companies have begun maneuvering for a share of the State Department's $4.4 billion plan to fortify U.S. embassies around the world, but some senators wonder whether the colossal building project might provide more of a windfall to contractors than security for Americans abroad.

A score of companies, including Bechtel and TRW Corp., are expected by mid-May to bid for a half dozen project manager positions, which the State Department will finance with $130 million in total service fees. That is in addition to the $3.4 billion budgeted for construction costs, and the $900 million allocated to beefing up communications security.

Altogether, the plan calls for building 79 new embassies or missions, reconstructing 175 more and renovating 10,000 residences overseas to be more resistant to terrorist attacks.

Because of a "buy American" policy, U.S. businesses will supply nearly everything except unskilled labor to even the most remote construction site. The products needed for the five-year effort range from granite blocks to new rugs to armored cars, as well as guard training and delicate electronic gear.

Sky-high cost estimates for some of the planned facilities have raised eyebrows on Capitol Hill. The General Accounting Office, after examining security projects now underway at U.S. facilities in 15 countries, recently reported habitual cost overruns, bungled construction work and serious security lapses -- and Congress is worried that such problems could recur on a much larger scale.

The Senate Foreign Relations Committee opens hearings Wednesday on the security improvement bill, which was drafted in response to a June 1985 panel headed by retired Adm. Bobby Inman, former head of the National Security Agency. It passed the House 389 to 7 last month, with few members eager to oppose the measure amid a flurry of terrorist activities abroad.

But some senators have reservations. For example, in a list of 105 questions, Chairman Richard G. Lugar (R-Ind.) and ranking minority member Claiborne Pell (D-R.I.) asked the State Department why the $33 million facility specified for Oman needed thick outer wall facings of a particular fine granite available only in Vermont.

Lugar and Pell said the State Department wants to put up buildings costing $20 million to $39 million in places such as Cotonou, Benin; Yaounde, Cameroon; Rangoon, Burma; Mogadishu, Somalia; and Chang Mai, Thailand. The $33.4 million for a new compound in Belize equals 20 percent of that country's gross national product, they noted.

"Do we really have to spend so much for facilities where we have very small staffs?" the senators asked.

"Construction costs bear little relation to the country's size, importance or GNP," the State Department replied. "Virtually all the materials contained in the building are imported from the United States."

Under the new plans, the department will spend $107 million to buy and ship U.S.-made furniture, lights, wallpaper and so on to its new and renovated embassies. The price is about double what the furnishings would cost without shipping, department officials said.

Sen. Jesse Helms (R-N.C.), demanded in a sheaf of 120 questions that the department "please explain what relationship there is between new office furniture . . . and protection against terrorism."

Senators also have expressed concern about reports that one of the prime bidders on the Oman project was a Greece-based construction firm owned by a Palestinian group, the Consolidated Contractors Co. The department replied that many foreign firms are bidders.

Sen. Edward Zorinsky (D-Neb.), asked the GAO to investigate reports that anyone with $1,000 can buy detailed architectural blueprints for any of the proposed buildings. "If true, this seems to be a very serious breach in security," Zorinsky said. In a separate statement, the senator said he backed "legitimate requests" to boost embassy security but objected to "feathering already well-appointed nests" of diplomats.

The massive construction project, which one interested corporation said has "no direct parallel in recent history," would drastically alter the lifestyles and workplaces of thousands of U.S. officials.

It also would put about 1,300 employes under a new Office of Diplomatic Security in the State Department and set up a special board to investigate security failures and fix blame. Intelligence community officials are concerned that the program could force them to answer to inexperienced bureaucrats within a new mini-empire at the State Department. A new security corps run out of Foggy Bottom would be responsible for protecting foreign diplomats in the United States.

Many firms put in preliminary proposals to handle all this months ago, long before Congress took up the idea. Although no company would comment on its submission, The Washington Post reviewed a copy of one offered by The Fluor Corp. and two other California firms.

They offered a preliminary "partnership plan" in which they would "function as an extension of the Department of State staff" to draw up a "master plan" of construction and set up a "systems integration and training facility" in Washington. The proposal promises to produce the kind of "vulnerability assessment" to guide planning at each site and provide "justification for requesting additional allocations."

The prospect of such "additional allocations" is what worries some members of Congress.

The GAO report on existing security efforts found "continued instances of disputes" among the State Department, other agencies, overseas posts and contractors over costs, plans and results. The study found that 13 security reconstruction projects budgeted at $177.5 million will now cost an extra $89 million because of delays.

"Even when completed, these buildings may not meet all current standards," the report said. For example, five will not have the 100-foot setback from the street that the State Department wants. A program to improve perimeter security at 70 posts was budgeted for $40 million, but contractors now say it will cost $91 million and cover only 37 posts, the study said.

Committee staff members said so many problems with only two or three projects a year raised questions about whether the State Department has the capacity to manage the ambitious new plans.

The GAO expressed "serious questions" about guard hiring, training and background check procedures. One embassy seeking to improve its security system last year called upon the cleaning crew it hired daily to guard the ambassador's residence. At another embassy, a school guard left his gun in a bathroom where a child found it. In Venezuela four years ago, a succession of contract guards quit in irritation when they were required to walk the ambassador's poodle.

Before Foreign Relations Committee staff member John Ziolkowski visited the Somalia site earlier this month to look at the State Department's $33.6 million construction plans there, the embassy cabled the department that $6.5 million could be saved by leasing or purchasing an existing building. State cabled back that "the question of construction, lease, purchase should not be raised" with Ziolkowsky "nor should [the Somalia] post change [cost] estimates."

The man trying to answer all these questions is Robert E. Lamb, assistant secretary of state for administration and security. He said in an interview that Congress shares the blame for construction delays by doling out only partial project funding every year.

While nothing in the plan would have prevented the recent shooting of a U.S. communications officer in Sudan, he said, training funds it provides might have helped him be a tougher target. Although terrorists will be likely to choose easier targets when embassy security is tighter, "it cannot be left to the individual to decide the amount of protection," he said.

He added that it is "a typical bureaucratic response" to say that such a huge undertaking should proceed slowly. "We are going to push them on that," he said. "These buildings are going to be up and occupied within three years of getting the money. That's a promise."