The Soviet Union has proposed to China that the two countries revive talks about improving relations or at least reopen low-key border negotiations that were broken off more than three years ago, according to well-informed sources here.

The proposals were relayed through diplomatic channels three weeks ago and were described by Soviet sources as an attempt to reestablish dialogue that could create conditions for some improvement in their relations.

A Chinese source here confirmed the Soviet overture but suggested that only the resumption of border negotiations was advanced.

From Peking, The Associated Press reported that the Chinese Foreign Ministry said, "We already have received a note calling for continuing negotiations from the Soviet Union. We always have believed in negotiations to settle the issues concerning the border . . . . We are studying the latest proposal."

The Kremlin's move follows a Chinese invitation in June for resuming the border talks.

The Soviets are believed to have advanced their proposal in a move to ease their isolation, following the opening of ties between Washington and Peking in 1979. The resumption of the border talks is not expected here to wipe out the intermittent bouts of name-calling and bitter resentments accumulated during the past two decades. Nor would it diminish Soviet concern at the way China has emerged into a rival communist giant.

But the Soviets believe that -- like the United States playing its "China card" to influence relations with Moscow -- the Kremlin could influence its relations with Washington by improving ties to Peking.

The border negotiations have been conducted intermittently in Peking for almost a decade until three years ago. They dealt with river navigation, border trade and border demarcation. The last problem led to bloody Sino-Soviet clashes in 1969. The talks were broken off in 1979 because of the Chinese objection to the Soviet invasion of Afghanistan.