The selection of Konstantin U. Chernenko as the new Soviet leader makes it doubly important that the United States be patient and consistent in seeking improved relations with the Soviet Union. The opportunity exists to produce better communication between the two superpowers, and, ultimately, a thaw in the current diplomatic chill.
But achieving such results will require not only a continuation of recent softened American rhetoric but also a new constancy from all US diplomats. It will take time for the highly skeptical Soviets to believe the US seriously seeks a better relationship. Yet there are definite reasons to believe improvement could ultimately be accomplished with Chernenko at the Soviet helm.
There should be no American expectation of immediate change, however. Officially appointed general secretary of the Communist Party, Mr. Chernenko can be expected to be slow to alter current Soviet policy, international as well as domestic, inasmuch as he is now in effective partnership with other members of the Soviet inner circle, and group decisions are usually cautious ones. Also, the majority of those members have shown their desire for little change in Soviet policies by selecting Chernenko, heavily identified with Leonid Brezhnev, whom he served for years as a top assistant.
Yet Chernenko has shown a desire for better relations with the United States, most recently in an article he wrote which appeared in The Times (London) on Sunday. ''We are in favor,'' he said, ''of an active and fruitful dialogue with nations living under a different social system to ours, the United States and Great Britain in particular.'' Finally, the Brezhnev years included detente between the Soviet Union and the US, and Chernenko at that time was considered a strong supporter of detente. It is now up to Chernenko and his associates to follow up the words with restraint in deeds.
At the same time Chernenko has served notice he will not be a pushover, saying in effect that he will not weaken the Soviets' military strength.
Through its appointment of Vice-President Bush the US was indicating a hope that the process of dialogue might begin Tuesday, with a brief Bush-Chernenko meeting after the Andropov funeral. In time perhaps that would lead to talks between the two top leaders.