WASHINGTON (AP) _ The Soviet Peace Fund will try to raise funds worldwide for victims of the Chernobyl nuclear power plant accident with a telethon on April 26, the fourth anniversary of the disaster, chess master Anatoly Karpov said Friday.

Karpov, the fund's chairman, said the 24-hour telethon will be broadcast from Moscow on Soviet state television, which is negotiating with American networks about the possibility of showing it in the United States as well.

He said preliminary agreement had been reached for broadcast in Japan and ''great interest'' had been shown in Central Europe. A toll-free number is being set up for people wishing to make contributions, but no specific goal has been set, he said.

''The children are suffering. They need your help now. If we can't help them, tomorrow is going to be late,'' said journalist Marat Yegorov, first deputy chairman of the Byelorussian Peace Fund.

Karpov and other members of the delegation spoke through a translator.

The telethon is being sponsored by the Soviet Peace Fund in association with the International Childhood Leukemia Association of Reston, Va., and Union Chernobyl U.S.A. of Anchorage, Alaska.

There has only been one previous fund-raising telethon in the Soviet Union, held in January by a children's welfare organization, Karpov said.

Dr. Leonid Kelner, executive director of the Leukemia Association, said estimates of the number of children suffering from leukemia as a result of the accident range from the tens of thousands to 160,000.

Karpov and others said the Soviet telethon would seek to raise funds, medical equipment and food for 1.5 million persons suffering because of high doses of radiation.

They said the telethon would reconstruct the chain of events in the first few days after the 1986 diaster at the Chernobyl nuclear sation. It will take viewers into the homes of people in the Ukraine and Byelorussia still suffering from the effects of the radiation, they said.

Soviet and foreign government officials, scientists, writers and artists will participate, they said. Soviet movie star Ludmila Gurchenka will be hostess.

The U.S. Information Agency arranged the delegation's visit to the United States, which also included stops at the United Nations and the Three Mile Island nuclear plant in Pennsylvania, the scene of an accident in 1979.