A better Soviet missile?

The Soviet Union may be making progress on developing a competitor to the American cruise missiles. So, at least, suggests a senior civilian official in Moscow, saying he understands there have been ''several tests'' of an improved Soviet cruise projectile.

In a conversation with the Monitor, he did not specify the nature of these tests, nor give details of the weapon being developed. Yet he left little doubt that the aim was to rival the small, radar-elusive cruise missile developed by the US.

''Now how will the Americans feel,'' he asked rhetorically, ''when any Soviet trawler . . . or surface ship . . . or airplane can have these cruise missiles?''

The official argued that the Americans were making the same mistake that marked the race to develop MIRVs, or multiple-warhead missiles, by avoiding a negotiated ban on cruise missiles on the erroneous assumption that the Soviets could not bridge a US technology lead.