The Soviet Union has called for U.S.-Soviet talks on a nuclear test ban to begin next month and has appointed a leading nuclear expert to head the Soviet delegation, a senior Soviet official said today.

Moscow imposed a unilateral ban on nuclear testing in August 1985 and is seeking Reagan administration compliance with it.

The bilateral talks could be held in Washington, Moscow or a third location such as Geneva, Deputy Foreign Minister Viktor Komplektov said at a press conference here today.

"The further destiny of the moratorium now hinges on the U.S.A.," Komplektov said.

Androiac Petrosyants, director of the Soviet atomic energy commission, will lead the Soviet team, he said.

Today's action appeared to mark one more step in a concerted Soviet campaign to pressure the United States into negotiating a moratorium on nuclear testing, according to western diplomats here. "It's an attempt to end run the White House's rejection of a test ban," one western diplomat said.

In Washington, Kenneth L. Adelman, director of the U.S. Arms Control and Disarmament Agency, said, "If they're talking about a meeting to discuss verification of a threshold test ban treaty, we welcome it. But if the proposal only applies to a comprehensive test ban, we're not interested at this time." staff writer Don Oberdorfer reported.

Komplektov, who heads the Foreign Ministry section dealing with American affairs, joined Gen. Nikolai Chervov, press spokesman Vladimir Lomeiko and other senior Soviet officials in the press conference to criticize the U.S. rejection of a test ban.

The Soviet spokesmen contradicted U.S. arguments that the test ban is not verifiable. The claim, nuclear expert Mikhail Sadovski said, "is out-and-out nonsense."

The spokesmen reiterated Soviet leader Mikhail Gorbachev's offer to let international on-site inspectors verify the moratorium and to accept the offer of six nonaligned countries to oversee the verification.

Gorbachev said yesterday that the Kremlin would extend its seven-month-old test ban, due to expire March 31, until the United States conducts its next nuclear test.

"We do not take pleasure in putting the United States in an embarrassing situation," Komplektov said. "We want to do business with them." He added, "We are willing to participate in any forum to move the complications of the test ban problem out of an impasse."

Komplektov, a candidate to succeed Anatoliy Dobrynin as Soviet ambassador in Washington, dodged questions about the possible appointment during the 90-minute press conference.