In a significant advance for the U.S. commercial space industry, Martin Marietta Corp. yesterday announced a novel agreement to launch 15 General Electric Co. communications satellites on unmanned Titan rockets over the next several years.

The deal establishes Martin Marietta as the dominant firm in a burgeoning domestic rocket business that has developed in the two years since the Challenger space shuttle disaster. Although yesterday's agreement provided no financial details, a senior company official said it could mean between $750 million and $1 billion in revenue for the Bethesda-based firm through the early 1990s.

Reagan administration officials and industry analysts hailed the agreement as a milestone in the government's effort to "privatize" space launch services, saying that it shows how U.S. companies are using innovative pricing strategies to snare business away from the French rocket firm, Arianespace, and other potential international competitors such as the Soviet Union and China.

"This is far and away the most substantial example of the U.S. industry's success in signing up customers," said Secretary of Transportation James H. Burnley, whose agency has actively promoted the space privatization efforts. "It's a major breakthrough."

Martin Marietta and GE have formed what amounts to a joint marketing agreement, in which potential customers -- such as telecommunications companies and foreign governments -- will be offered substantial discounts and special scheduling breaks if they agree to launch their GE-built satellites aboard Martin Marietta's Titan rockets.

"This may be the first salvo in a frequent-flier type competition," said Brad Meslin, managing director of CSP Associates, a Cambridge, Mass., space consulting firm. "It's really a coming of age for the commercial launch services industry."

The agreement is the second big announcement in four days for Martin Marietta and a powerful boost for the firm's efforts to position itself as a high-technology space age company. Only last month, the firm was shaken by its loss to Boeing Aerospace in a bid to become a prime contractor on the National Aeronautics and Space Administration's space station. But it rebounded last Friday when it won a $508 million Pentagon contract to build a national computerized facility that will test and evaluate proposals for the Strategic Defense Initiative.

With the GE agreement, analysts said, the firm has gained a clear edge over its two U.S. rivals, McDonnell Douglas Corp., maker of the Delta rocket, and General Dynamics Corp., maker of the Atlas Centaur rocket, although the world market to launch satellites is dominated by Ariane. The Titan, which Martin has long made for the Air Force to launch heavy military reconnaissance and other satellites, has substantially greater payload capacity than its two U.S. competitors, although it cost more than twice as much to launch -- $110 million per flight, compared with about $50 million a flight for a Delta.

"Certainly, in terms of intent to fly payloads on a given launch vehicle, it clearly establishes us as the U.S. market leader," Norman R. Augustine, Martin Marietta's vice chairman and chief executive, said in an interview. "It gives us a base ... and from GE's standpoint, it assures them they will have preferred access to a very reliable, and the largest, payload carrier {the Titan} in the free world."

Augustine stressed, however, that the agreement represents GE's "intent" to fly aboard Titan, but does not guarantee those flights. Under the agreement, some of the 15 GE satellites can still fly aboard Ariane or other rockets, although GE will be required to pay penalties if that happens, Augustine said. "So I don't want to make this sound like it's a guaranteed, ironclad, sure thing that we're going to launch these 15 Titans."

"While the Titan will be the preferred launcher for GE launches, GE will continue to be totally responsive to customer's wishes or program requirements for alternative launch vehicle selections," said Charles A. Schmidt, vice president and general manager of GE's Astro-Space Division in Princeton, N.J., which is building the satellites.

Coming on the eve of the second anniversary of the Challenger accident, the agreement underscores the dramatic changes in the U.S. space program spurred by the accident. Attempting to promote the shuttle as an all-purpose and ultimately self-financing space truck, NASA had offered to launch commercial satellites aboard the shuttle at far below cost, thereby keeping private rocket companies out of the market.

But as part of its space-program recovery plan first disclosed in August 1986, the Reagan administration moved to privatize launch services and ordered NASA to remove all commercial satellites from the shuttle manifest. As a result, three firms -- Martin, McDonnell Douglas and General Dynamics -- have entered the business and begun competing with the market leader, Arianespace.

McDonnell Douglas has signed contracts to launch at least two satellites -- one owned by a British firm and another by Inmarsat, the International Maritime Satellite consortium -- aboard its Deltas. General Dynamics has signed an agreement to launch a European telecommunications satellite, while Martin had announced four earlier agreements to launch satellites for the British, the Japanese and the International Telecommunications Satellite Organization (Intelsat).

The flights are scheduled to begin sometime next year from Cape Canaveral. "Without the {Reagan administration's} policy change, none of this would be happening," said Burnley.

The administration was supposed to announce a new space policy yesterday that would provide further encouragement for private enterprises in space, such as commercial experiments and small-scale space stations. But at the last minute the White House postponed a briefing on the subject because of what sources described as conflicts among presidential advisers.

"Our anticipation {in setting up the briefing} was that all decisions would have been made and they have not," said White House spokesman B.J. Cooper.