After the initial attempts to reach a comprehensive agreement failed, the Soviets tried to limit negotiations to anti-ballistic missile systems and said restrictions on offensive systems should be postponed. The American position was that limiting ABM systems, but allowing full growth of offensive weapons, would be inconsistent with SALT`s core objectives and that it was important to make at least a start in limiting offensive systems. A long deadlock on this issue was finally broken by trade at the highest levels of both governments. On May 20, 1971, Washington and Moscow announced that an agreement had been reached to focus on a permanent contract limiting ABM systems, while extending certain restrictions on offensive systems and continuing negotiations for a broader and long-term agreement on them. The SALT II Treaty banned new missile programs (a new missile defined as a 5% larger missile than the one currently used), so both sides were forced to limit their development and the construction of new types of strategic missiles, such as the development of additional fixed iCB launchers. Similarly, the agreement would limit the number of mirved ballistic missiles and long-range missiles to 1,320.  However, the United States retained its most important programs, such as the Trident rocket, with cruise missiles that President Jimmy Carter wanted to use as his main defensive weapon, because they were too slow to have a first strike capability. In return, the USSR could retain only 308 of its so-called « heavy ICBM » SS-18 launchers. Through diplomatic channels in Washington and Moscow, discussions with Soviet representatives within the ENDC and exchanges at the highest level of the two governments, the United States continued to insist on the Soviet obligation to discuss the strategic limits of armaments. But it was not until the following year that evidence of a Soviet reassessment of their position emerged. On 1 July 1968, at the signing of the Non-Proliferation Treaty, President Johnson announced that an agreement had been reached with the Soviet Union to begin talks on limiting and reducing strategic nuclear weapons and ballistic missile defence systems. The date and location of the talks had not yet been announced when the Soviet Union began its invasion of Czechoslovakia on 20 August, an event that postponed the talks indefinitely. On May 27, President Reagan announced that the United States would no longer respect the treaty`s limits.
The President stated that the USSR had not respected its political commitment to respect the provisions of the treaty and had not demonstrated its willingness to obtain further agreements on arms reductions.