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. On June 18, 1979, an agreement to limit strategic launchers was reached in Vienna, signed by Leonid Brezhnev and Carter at a ceremony in the Redouten Hall of the Imperial Hofburg.  The Strategic Arms Reduction Treaty (START I), first proposed in the early 1980s by President Ronald Reagan and finally signed in July 1991, required the United States and the Soviet Union to reduce their strategic arsenals to 1,600 delivery vehicles, which bore no more than 6,000 warheads, as they were counted according to the rules of the agreement. The agreement required the destruction of surplus delivery vehicles, which were verified through an intrusive control system including on-site inspections, regular exchanges of information (including telemetry) and the use of national technical means (e.g. satellites). The entry into force of the agreement was delayed for several years due to the collapse of the Soviet Union and subsequent efforts to de-incarcerate Ukraine, Kazakhstan and Belarus, returning their nuclear weapons to Russia and making it part of the non-proliferation and launch I agreements. Start I reductions were completed in December 2001 and the contract expired on December 5, 2009. START II On April 8, 2010, the United States and Russia signed New START, a legally binding and verifiable agreement that limits each side to 1,550 strategic nuclear warheads, used by 700 strategic delivery systems (ICBMs, SLBMs and heavy bombers), and launchers used and unused to 800.
The warhead limit responsible for the contract is 30 percent below the SORT 2200 limit and the limit for delivery vehicles is 50 percent lower than the 1,600 permits in START I. The contract has a verification system that combines elements of START I with new elements adapted to New START. Treaty measures include field inspections and exhibitions, data exchange and notifications of strategic offensive weapons and facilities under the treaty, as well as provisions to facilitate the use of national technical means of contract monitoring. The treaty also provides for the continuous exchange of telemetry data (missile test data for up to five tests per year) and does not usefully limit missile defence or conventional long-range attacks. The U.S. Senate approved New START on December 22, 2010. The approval procedure of the Russian Parliament (passage of both the Duma and the Council of the Federation) was completed on 26 January 2011.