Soviets Stage 16th Underground Nuclear Test Since Moratorium

MOSCOW — The Soviet Union detonated an underground nuclear device Friday in its 16th nuclear test since abandoning a unilateral moratorium last February, the Tass news agency reported.

The test came as Soviet Foreign Minister Eduard A. Shevardnadze held talks in Washington that resulted in the superpowers reaching agreement in principle on a treaty banning U.S. and Soviet intermediate-range nuclear missiles.

As part of the negotiations, U.S. and Soviet spokesmen announced Thursday that the two sides would begin full-scale negotiations by Dec. 1 to end all nuclear weapons tests.

Both sides said effective verification would be a key to any agreement to ban nuclear testing.

Tass said the Friday blast at the Semipalatinsk test range in Soviet Central Asia had a yield of up to 20 kilotons. One kiloton is the equivalent of 1,000 tons of TNT.

The news agency said the explosion was “carried out with a view to upgrading military technology,” but gave no details.

Soviet leader Mikhail S. Gorbachev began the moratorium on his country’s nuclear weapons testing program on Aug. 6, 1985, the 40th anniversary of the American atomic bombing of Hiroshima, Japan.

Despite Gorbachev’s appeals, the United States refused to join the moratorium. It said further tests were needed to check the effectiveness of nuclear weapons and to develop the “Star Wars” defense against nuclear attack.

The Soviets resumed testing on Feb. 28.