BACKGROUND: SALT, START and SORT: US-Russia arms control

Feb 6, 2009, 15:40 GMT

Munich - The nuclear balance between the United States and Russia, discussed at the Munich Security Conference Friday, is maintained by a patchwork of treaties limiting the construction and deployment of strategic weapons, with some of the treaties on hold.

With the election of US President Barack Obama, experts say that there is now a chance of negotiating a comprehensive deal.

SALT: The process began with the Strategic Arms Limitation Talks (SALT), which ran between the US and the Soviet Union throughout the 1970s and were aimed at limiting the stockpiling of nuclear arms.

SALT-I, signed in 1972, capped the number of land- and submarine-based missiles and nuclear bombers either side could deploy at the then-existing levels. It also led to the signature of a treaty limiting the use of anti-missile systems, known as the ABM treaty.

SALT-II, signed in 1979, capped the number of multiple-headed nuclear missiles either side could hold at 2,250. The US pulled out of SALT-II in 1986, saying that the USSR had breached its terms.

START: At the same time, the two superpowers re-launched talks aimed at cutting their nuclear capability.

The Strategic Arms Reduction Treaty (START-I), signed in 1991, committed both sides to reducing their arsenals by some 30 per cent, leaving a maximum of 1,600 missiles with no more than 6,000 warheads. START-I is set to expire on December 5.

Following the collapse of the USSR, the US and Russia agreed to a second round of nuclear cuts, known as START-II. The treaty roughly halved the number of warheads each side could hold and banned multiple-headed missiles entirely.

However, by the time Russia ratified START-II in 2000, the US was threatening to pull out of the ABM treaty in order to build a new anti-missile system aimed at defending the country against 'rogue states.' Russia saw such a move as a threat to its own deterrent.

The US pulled out of the ABM treaty on June 13, 2002. Russia pulled out of START-II one day later.

SORT: simultaneously, the two sides agreed to the less ambitious Strategic Offensive Reductions Treaty (SORT), signed in Moscow in May 2002. SORT caps the number of warheads each side can hold at 2,200, but imposes no verification mechanism and allows the two sides to mothball warheads so they can be re-activated later.

SORT is set to expire on the last day of 2012.