Senator Metzenbaum said he would ask the Senate Judiciary Committee to approve legislation barring domestically manufactured assault weapons when it meets next Thursday.

Asserting that domestic assault weapons were ''favored by drug dealers and street gangs,'' he added, ''Any police officer will tell you it doesn't matter if you are killed by an imported or American-made assault weapon -you are just as dead.''

Semiautomatic rifles are those that require no manual action except a separate trigger pull to fire each bullet. Automatic weapons like machine guns fire a stream of bullets with a single trigger pull. President Shifts Stand

In the Presidential campaign last year Mr. Bush, a hunter and longtime member of the N.R.A., opposed to any bans on assault weapons. But a public outcry after a drifter armed with an AK-47 killed five schoolchildren in Stockton, Calif., in January helped convince others in the Administration that some limits were needed.

At the urging of William J. Bennett, the director of national drug control policy, the Administration suspended imports of certain types of semiautomatic assault rifles in March. The President expanded that temporary ban as part of a broader anticrime program that he announced in April, and said he would make it permanent for imported weapons that did not have a legitimate sporting use.

The 43 types of semiautomatic rifles now barred from entry into the United States were part of a group of 50 evaluated by the firearms bureau in a three-month study. The bureau has authority under the 1968 Gun Control Act to block imports of weapons not generally suitable to sporting use, but it does not regulate domestic manufacture of weapons.

Mr. Higgins said the bureau concluded that there were ''viable, clear differences between semiautomatic assault rifles and semiautomatic rifles used in traditional sports.'' Some distinguishing features of assault-style weapons, he said, are the ability to accept a detachable magazine and a centerfire cartridge that is less than 2 1/4 inches long. Six Rimfire Rifles Exempted