Tucked inside Pentagon and Kremlin planning documents are the beginnings of an arms race that may have greater significance and be more difficult to stop than the race for nuclear superiority.
This is the growing capability of the two superpowers to wage ''space wars.'' It's a development that is accompanied by arms-control ramifications as complex and difficult as the antisatellite missiles and lasers proceeding toward deployment.
The Soviet Union has already developed and tested in space an antisatellite (ASAT) weapon launched from Earth, and US officials say it is spending three to five times as much as this country on high-energy laser weapons research.
''Based on the evidence available to us, it is clear that the Soviets have a massive military space program,'' warns Richard Delauer, defense undersecretary for research and engineering.
But the United States is catching up in its development of antisatellite missiles launched from jet fighters, as well as with lasers that could cripple an opponent's command, control, and intelligence-gathering satellites. The Pentagon plans to increase its space-system spending by 20 percent per year (after inflation) over the next three years.
The Outer Space Treaty of 1967 prohibits the basing of ''weapons of mass destruction'' in space. But as all nations become more dependent on satellites for everything from crop planning and military command to arms-control verification, it becomes evident that this and similar treaties do not address lesser weapons that could significantly harm a country without ever reaching Earth.
This realization was at the heart of President Reagan's national space policy announced in last July and followed up with directives for proceeding with such things as ASAT weapons designed to ''deny any adversary the use of space-based systems that provide support to hostile military forces.''
Soviet-US talks on limiting space weapons have been stalled for nearly three years. The USSR last fall at the United Nations offered a draft space treaty banning the stationing of weapons in space. But it did not define a ''weapon,'' nor did it address the especially difficult subject of verification. The US has yet to respond to this offer.
''We certainly don't want another competitive arms race in a new and expensive sector of the military,'' US Arms Control and Disarmament Agency director Eugene Rostow told a Senate hearing last week.
But, he adds, ''It would be the height of folly to rush into negotiations on these subjects unless we are ready with verifiable proposals that will enhance national security.''
Senate arms-control subcommittee chairman Larry Pressler (R) of South Dakota says he senses here a ''stickiness, a slowness, a reluctance, a half-heartedness'' on the administration's part to control weapons in space.
''At the moment there appears to be no serious attempt to foreclose a competition in destruction of space systems that surely looms in the longer run if it is not immediately prevented,'' says John Steinbrunner, director of defense studies at the Brookings Institution.
Dr. Steinbrunner notes ''all space assets are inherently vulnerable to deliberate attack,'' and ''the explicit rationale under which we are deploying some of our most important space systems is quite provocative to the Soviet Union and invites attack on those systems.''
''I don't believe there's an arms race in space per se,'' responds Robert Cooper, director of the Pentagon's Defense Advanced Research Projects Agency. But, Dr. Cooper adds: ''I believe that our national interests in space will continue to expand. And wherever the country has national interests, it has national security interests.''
Essentially, the US position is that it is responding to a Soviet lead in space weapons, and that it must do so for deterrent purposes as well as to negotiate from a position of strength.
''The use of space by the Department of Defense should not be interpreted to mean that the US is 'militarizing' space, as some claim,'' Dr. Delauer told Senator Pressler's subcommittee last week. ''Yet . . . given the alarming rate of Soviet spending for space activities, it would be imprudent for us not to be prepared to defend our interests there, as anywhere else.''