General Motors Corp. has completed the first phase of an ambitious diversification strategy intended to make the auto maker the world's leader in advanced high technology, as well as in computer and financial services.

With its winning bid to acquire California-based Hughes Aircraft Co., GM yesterday moved into position to gain at least 10 percent of its global revenue from nonautomotive sources -- a goal announced by GM Chairman Roger B. Smith one year ago.

But some financial and auto industry analysts fear that GM might have hurt itself in its multibillion-dollar drive to grow by acquisition. The auto maker may be forced to cancel some pending diversification plans, or to reduce the scope of a few of its new-car programs, to soften the impact of the heavy spending it has done over the past year, those analysts said.

Other analysts disagreed. They said that GM has made all of the right moves and that if the car manufacturer is as successful in streamlining production at Hughes as it has been in reaching its early diversification objectives, GM could well become the nation's biggest, lowest-cost defense contractor.

The stock market seemed to support the optimists. GM yesterday closed at 72 1/8, up 5/8 on the New York Stock Exchange.

"I'm impressed with GM, and I'm impressed with Roger Smith," said James A. Mateyka, a vice president and auto industry analyst in the Washington office of Booz-Allen & Hamilton Inc. "They said what they were going to do, and they went ahead and did it. They clearly are thinking much more strategically at GM than they were thinking 10 years ago," Mateyka said.

Smith, since assuming the GM chairmanship on Jan. 1, 1981, repeatedly has said he wants to use the company's tremendous financial and organizational clout to move into other fields, particularly advanced high technology, defense and computer services.

"Our growth in the high technology field may come from inside or outside of the corporation," he said in June 1984. "We're going to stay loose and be very flexible about this. But, wherever the growth comes from, I hope to see GM grossing at least 10 percent of our sales in nonautomotive areas by 1990.

"In fact, 10 percent might even be a low figure," Smith said.

GM went on a buying binge, gaining equity in small companies, such as Teknowledge Inc., a California-based operation specializing in "artificial intelligence" -- expert computer systems that can think and draw like an engineer, or that can solve complicated procedural problems related to the design, development and manufacture of automobiles.

GM's high-tech purchases served a twofold purpose: to help the auto maker move ahead faster in its traditional business and to aid it in developing products, services and manufacturing processes that would be profitable outside of the auto industry.

In October 1984, GM took a major step toward achieving those synergies. The auto maker signed a $2.55 billion deal to acquire Dallas-based Electronic Data Systems Corp., one of the nation's biggest computer services firms.

Now EDS is being called upon to design computer systems for GM's ultra-modern auto plants and to help the auto maker move into the mortgage service industry. EDS already is playing a major role in the development of Saturn Corp., a newly formed GM subsidiary that the auto maker says will revolutionize small-car production in the United States.

If GM succeeds in using EDS's expertise to reduce the costs of auto production and increase the company's nonautomotive dollars, GM easily could exceed Smith's goal for 10 percent nonautomotive earnings by 1990, GM officials said yesterday.

About 96 percent of GM's $83.9 billion in worldwide sales last year came from the company's traditional automotive businesses. An estimated $1.3 billion, or about 1.5 percent, came from defense and aerospace. The rest flowed from an assortment of sources, including real estate and financial services.

"Hughes will give GM the ability to reduce its automotive revenue base to 90 percent," said David Healy, an analyst with New York-based Drexel Burnham Lambert. "But, in my thinking, that is a relatively modest diversification when you look at what they're paying to get Hughes," Healy said.

GM said it is spending more than $5 billion to get the defense-aerospace company, which last year had sales of $4.9 billion and a net income of $80 million.

That seems the wrong thing to do "at a time when Congress is looking with disdain at defense companies," said Arthur G. Davis, an analyst with Cleveland-based Prescott Ball and Turben.

"Defense spending will level off in about 1987," Davis said. But he said that GM could bring its manufacturing techniques to Hughes and use EDS "to gain other efficiencies." The combination "could help GM become the low-cost producer in defense, which means that it could get more defense business and help Hughes to grow even in a flat market for defense," Davis said