President Carter will seek to negotiate with the Soviet Union a five-year ban on any kind of underground nuclear test explosions, administration officials said yesterday.
Carter, in making that decision last Saturday, put provisions in his memorandum that the administration hopes will soften the opposition of the Joint Chiefs of Staff to such a complete ban.
One provision, sources said, states that testing definitely will resume after five years unless the chiefs agree to continuation of the ban.
Air Force Gen. David C. Jones, selected by Carter to be chairman of the joint chiefs, told the Senate Armed Services Committee at his recent confirmation hearings that "I would have difficulty recommending a zero test ban for an extended period."
The chiefs, after first opposing any ban outright, recommended a three-year pact, sources said. Carter is hopeful of getting the chiefs to go along with a five-year suspension.
The executives of laboratories which develop nuclear warheads conferred with the chiefs earlier this month and expressed their opposition to "zero" underground testing. The lab executives said a warhead failed to explode in a recent underground test, showing the need for continuous testing, sources said.
Opponents of a complete ban aruge that the Soviets could cheat by setting off small, muffled, underground test explosions which the United States could not detect. They contend this would enable the Soviets to improve their weaponary clandestinely while the United States stood still in the pursuits of better warheads.
Backers of the ban counter that detection equipment is so good now that the risk of test explosions going undetected is minimal. The ban would help slow down the arms race between the two superpowers, they contend, as well as help curb the spread of nuclear weapons to other nations.
One idea Carter rejected was to permit both the United States and Soviet Union to set off small nuclear explosions - less than five kilotons - underground.
Prospects for a complete test ban brightened last year when the Soviet Union, which had been planning to set off nuclear explosions for civil improvements, said it was willing to suspend all kind of underground nuclear blasts.
An underground explosion to dig a canal could not be distinguished with certainty from one designed to improve a warhead, and might be used to conceal a weapon test, critics of a complete ban have argued. The Soviet policy change on peaceful explosions removed this obstacle to the total ban.
Administration officials acknowledged yesterday that they will run into the same kind of heavy opposition in their pursuit of "zero" testing as they have encountered on their strategic arms control proposals to the Soviet Union.
The opposition stems from the contention that the United States must move ahead vigorously in weapons research and deployment to offset the Soviet arms buildup. Carter pledged while running for president that he would try to negotiate a comprehensive test ban.
The United States and Soviet Union in 1963 signed a treaty, which the Senate ratified, prohibiting nuclear explosion in the atmosphere, outer space and under water. The stated common goal was to put an "end to the contamination of man's environment by radioactive substances."
In 1974, the United States and Soviet Union signed the Treshold Test Ban Treaty to prohibit underground nuclear tests exceeding 150 kilotons. A related treaty, signed by the two superpowers in 1976, established rules for setting off nuclear explosions for peaceful purposes. Both treaties have been pending in the Senate since July 29, 1976.