WASHINGTON – U.S. President George W. Bush‘s decision to withdraw from the Anti-Ballistic Missile Treaty marks the first time in recent history that the United States has abandoned a major international pact and caps a multiyear campaign by hard-line Republicans to end missile defense curbs. Bush and his top aides have long indicated such a move was likely if the United States could not reach compromise with Russia, the other major nuclear power who is partner to the 1972 Cold War pact.

But his formal decision, announced on Thursday, is a watershed, with critics fearing it could propel the unraveling of an international arms control regime that has helped keep peace for half a century. It is significant that a Republican president is taking action since recent Republican presidents have essentially built the arms control regime Bush is accused of dismantling.

Many critics, including opposition Democrats and European allies, are further unnerved because Bush this year also torpedoed international efforts to strengthen a treaty banning biological weapons and a treaty putting limits on fossil fuel emissions.

Bush, backed by many Republican foreign and defense heavyweights, has made clear since he was a candidate in 2000 that he saw the ABM Treaty as a relic of the Cold War, curtailing development of a defense shield against incoming enemy missiles that has been a Republican dream since Reagan. The pact rests on the principle of mutually assured destruction — the idea that neither Washington nor Moscow would launch a nuclear attack because of certain massive retaliation. To assuage fears that U.S. missile defenses would leave Russia‘s nuclear arsenal vulnerable to attack, Bush agreed with President Vladimir Putin to sharply reduce their stockpiles. To calm fierce opposition from Russia and the Europeans, the United States tried finding a way with Moscow that would allow the United States to vigorously test and build missile defenses while preserving the broad outlines of the treaty, which Russia insists is a cornerstone of nuclear stability.

On Wednesday, some critics held out hope that negative reaction to Bush‘s decision would persuade him to hold further negotiations with Moscow. But Bush aides said further talks on missile defense were unlikely. Reuters