President Reagan's freshly reaffirmed ''strategy for peace'' depends on how the new Soviet leadership responds to his concept of arms buildup as a spur to arms reduction.
If only Moscow could muster the courage to do what would earn it the gratitude of all future generations: simply accept the US arms-cut proposals in the certainty that each side would retain enough nuclear overkill to deter attack by the other indefinitely. Such a bold rejoinder would require the US to forgo new missiles in Europe and permit the controversial MX to go undeveloped.
The Kremlin missed a previous opportunity to earn the world's gratitude when it rejected out of hand the ineptly presented but forward-looking arms reduction proposals of the Carter administration in 1977.
But now the Soviets are reported to have proposed similar reductions themselves in the START negotiations. They could go further, especially in an atmosphere of mutual superpower respect. Mr. Reagan sounded a welcome conciliatory note by praising their START position as a ''serious'' one.
The question is how serious the Russians will take Mr. Reagan to be. There may be some hope for mutual understanding in Soviet leader Andropov's speech almost at the same time as Mr. Reagan's. He, too, proclaimed a willingness to negotiate while keeping up his nation's military might.
Insofar as the two leaders share a strategic outlook beyond their rhetoric, they ought to be able to get together on at least the confidence-building measures proposed by Mr. Reagan. These include exchange of data on nuclear forces, improvement of the hotline for emergency communications, and advance notice of military exercises and missile launch tests. Such steps could help forestall conflict based on misunderstanding.
Mr. Reagan also asks to be taken seriously on his proposal for the $26 billion MX weapons system to be deployed in Wyoming. He argues that it is needed as an incentive for the Russians to negotiate away other arms.