THE Anti-Ballistic Missile (ABM) treaty is either an ugly cold-war relic, or a bulwark against the re-emergence of hot nuclear dangers, depending on where you stand in one of America's sharpest policy debates. Signed in 1972, the accord was intended to stabilise the American-Soviet stand-off by entrenching each side's ability to wipe the other out. As amended in 1974, the treaty permits each side only one limited ABM system. It also rules out ABM systems at sea, in the air or in space.
American conservatives have long argued that the Soviet side broke its word; it built bigger ABM networks than the treaty allowed, and anti-aircraft defences whose second, secret aim was to stop missiles. In any event, say the critics, any purpose the treaty once served—during the cold-war game of Russian roulette for two—has been superseded by the emergence of multiple threats. When the Soviet Union collapsed, the treaty died with it: good riddance.
The treaty's supporters retort that tearing it up would prompt outrage in Russia at a time when it feels vulnerable because of its mouldering regular forces. Viewed from Moscow, the treaty's death might allow America to protect itself so well from the ex-Soviet arsenal that Russia could be attacked with impunity.
The Clinton administration wants to keep the treaty alive, but accepts it needs altering. It has already negotiated two changes: one raises the number of parties on the “Soviet” side to four (Russia, Ukraine, Belarus and Kazakhstan); the other broadens the definition of “theatre” missile defences, which the treaty allows. Sensing a chance to kill the treaty, Republican legislators are demanding the right to scrutinise these amendments. Bill Clinton says he will not send them to Capitol Hill until Russia ratifies the START-2 accord on slashing long-range arsenals.
In June, Boris Yeltsin told Mr Clinton that he was ready to discuss even broader changes to the agreement. This raised the prospect that America could construct a limited missile shield for itself while still observing the treaty. The keenest backers of anti-missile defences are dismayed; they are opposed to any policy that serves to keep the accord alive.
A side-effect of this stalemate might be a further breakdown of the non-proliferation regime that has kept the number of nuclear-armed states to less than a dozen. Under this regime, most countries refrain from going nuclear, on the understanding that the “superpowers” will negotiate arms cuts in good faith. With START-2 bogged down by arguments over missile defence, would-be proliferators can argue that the big powers have already breached the second part of this bargain.