WASHINGTON (AP) _ A veteran White House adviser says there is only a small chance the United States will retire enough nuclear weapons to put the country back into compliance with the SALT II nuclear arms treaty.

The United States breached the unratified 1979 treaty last week and Paul Nitze, a senior adviser to President Reagan, defended that decision Thursday in an appearance before the House Armed Services Committee.

Nitze was asked about the chance that enough U.S. weapons might be dismantled to put the nation back under the numerical limits in the treaty.

''I think it's small,'' answered Nitze, a veteran of the national security field and a long-time critic of past arms control efforts.

Nitze defended Reagan's decision, originally anounced last May, to break the treaty by saying its ceilings ''turned out to be unilateral limits'' on the U.S. nuclear arsenal because the Soviets violated it.

Nitze's defense of last week's action by the Reagan administration was met by criticism from committee Democrats.

Rep. Les Aspin, D-Wis., chairman of the armed services panel, said the move came ''at a time when the administration needs all the help it can get'' because of controversy over the sale of weapons to Iran and diversion of the profits to Nicaraguan rebels.

Rep. Norman Dicks, D-Wash., criticized the action and said Reagan had given ''the back of his hand'' to bipartisan efforts to narrow arms control differences between Congress and the White House.

The Pentagon last Friday put into service the 131st B-52 bomber modified to carry nuclear-tipped cruise missiles. That put the United States over the limits of various types of nuclear arms permitted by the treaty.

The treaty was never ratified by the Senate and even though Reagan criticized it, he pledged to observe its limits as long as the Soviets did likewise. But Reagan said in May it would be breached because the Soviets were violating the treaty.

Last week's action was criticized by U.S. allies in Europe and Democrats in Congress, who argued it made no sense to break the treaty's limits while the United States was trying to negotiate new U.S.-Soviet treaties.

Shortly before Reagan's October summit meeting in Iceland with Soviet leader Mikhail Gorbachev, Congress acceded to Reagan's appeal for unity and dropped an effort, which Dicks helped lead, to require continued compliance with SALT II.

''This administration has not done much for bipartisanship,'' Dicks told Nitze. ''I think you ought to take that back (to the White House). ... Bipartisanship has failed and it's the administration's fault. Congress has gone the extra mile.''