As its name implied, the Interim Agreement was intended as a transition toward a more comprehensive accord. Work began in November 1972 to forge a permanent comprehensive agreement and to correct the perceived flaws of the first accord. At the outset, negotiators hoped to sign the SALT II accord quickly. But their original optimism soon faded.

As the Watergate scandal created distraction and discontinuity in the Executive Branch, and east-west relations soured over such issues as the fall of South Vietnam and the Angolan civil war, the negotiations virtually stalled. The introduction of new weapons systems also complicated the arms control equation, as long-range air-launched cruise missiles (ALCMs) entered the American strategic weapons inventory and the Soviet Union deployed long-range Backfire bombers.

After years of tedious, complex negotiations, President Carter and General Secretary Brezhnev signed the SALT II agreement in Vienna on June 18, 1979. The accord limited each side to 2,400 launchers, which included ICBMs, submarine-launched ballistic missiles (SLBMs), heavy bombers, and air-to-surface missiles. SALT II included provisions banning construction of additional ICBM launchers, limiting the number of warheads each missile was allowed to carry, and imposing ceilings on missile size and payload.

The U.S. Senate never ratified SALT II, however, and President Carter withdrew the agreement from consideration in the wake of the December 1979 Soviet invasion of Afghanistan. However, both President Carter and successor Ronald Reagan declared that the United States would do nothing to violate the unratified accord so long as the Soviets acted likewise.