American officials have effectively blocked a bold move by the Soviet Union to use its own rockets - for a comparatively modest price - to launch Western satellites.
The Soviets offered to ''sell'' their rockets to Inmarsat, an international satellite organization based in London, for launching a new generation of satellites later in the 1980s.
Inmarsat runs a network of communications satellites that route telephone calls and data among some 2,300 ships and their shore bases. It has still to decide on the companies that will supply the new satellites, which could number up to nine and cost a total of $500 million.
But the satellites will certainly contain a large proportion of American parts. And under Moscow's bid the satellites would have to travel to the Soviet rocket site prior to the launch into space.
That is what the United States State Department objects to. The department says that ''under no circumstances'' would it permit the transfer to the Soviet Union of American-made satellite components. The transfer would be prohibited under the technology control regulations that seek to stop the channeling to unfriendly countries of hardware that could be used in weaponry.
Only two organizations have submitted tenders to Inmarsat to build the satellites. Both are consortia that include powerful American interests.
Hughes Aircraft Corporation of the US has teamed up with British Aerospace in one venture. The main members of the second consortium are Marconi of Britain, Aerospatiale of France, and Ford Aerospace of the US.
The consortia revealed themselves when submissions for the satellite contract were finalized at the beginning of April. Inmarsat, which is owned by about 40 countries and has annual revenues of some $40 million, says it will decide by early next year which consortium will build the new craft.
But the organization's wish to make a free choice over the launch vehicle for the satellites has been dealt a blow by the US move. The Soviet Union told Inmarsat last year that its Proton rockets, used by Soviet space engineers to ferry their own satellites and manned capsules into orbit, would be available for a fee of about $23 million a launch.
That is roughly half the comparable charge for a satellite launch by either the American space shuttle or the Ariane rocket sold by Arianespace, a semipublic company dominated by French interests.
Inmarsat told organizations wishing to bid for the satellite contract that the vehicles could be put into space by any of six launch craft - the Proton, Ariane, and the shuttle, together with three rockets sold by private companies in the US. These rockets are the Delta, Titan, and Atlas Centaur.
In the rules drawn up by Inmarsat for the tenders, companies submitting bids were asked to indicate the launchers they especially favor. But the final choice of which of the six launchers to use remains with Inmarsat.
The action by the State Department is in line with moves by the US government to block sensitive technology from falling into the hands of the Soviet Union.
Satellites act as telecommunications switchboards in the sky. They contain electronic components that could be useful to the Soviets' military buildup.
US officials fear that shipment to the Soviet Union's main launch site at Baikonur in Central Asia of hardware containing such components could provide Soviet military experts with useful information.
The declaration by the State Department could lead to repercussions within the ranks of Inmarsat, which, since it was set up in the late 1970s, has managed to avoid political arguments. The US is the biggest shareholder in the organization with 23 percent of the stake. The next biggest shareholders are the Soviet Union (14 percent) and Britain (10 percent).