U.S. and Pakistani officials fear a heavy loss of life from landmines left behind by Soviet troops withdrawing from Afghanistan and have appealed to Moscow for help in locating them, sources said Saturday.

One Western diplomat said the United States had asked the Soviet Union through direct appeals and through the U.N. envoy on Afghanistan, Diego Cordovez, for maps of minefields but described Moscow's response as "vague."Washington believes the Soviets, whose 1979 invasion has cost the Afghan nation an estimated 1.3 million lives, "has a major responsibility to take their mines with them . . . and to turn over their maps," he said. "They haven't done that."

The presence of anti-personnel mines is of special concern to relief agencies, including the United Nations High Commissioner for Refugees, which will be largely responsible for the eventual repatriation of millions of Afghan refugees in Pakistan and Iran.