WASHINGTON (AP) _ The United States notified the Soviet Union on Monday it will begin destroying rocket motors from Pershing II nuclear missiles on Sept. 8 in Texas.

The Defense Department, in a brief statement, said the notice was forwarded to Moscow in accordance with the terms of the Intermediate-range Nuclear Forces treaty.

That treaty, which became effective earlier this summer, requires the superpowers to dismantle and destroy the intermediate-and shorter-range nuclear missiles in their arsenals. The United States has two such types of missiles - the ground-launched cruise missile and the Pershing II.

Destruction of the solid-fuel rocket motors for the Pershing II missiles will begin on Sept. 8, ''weather permitting,'' at the Longhorn Army Ammunition Plant near Marshall, Texas, the Pentagon said. The motors will be destroyed through ''static firing.''

In a static firing, the motor is bolted into a concrete and steel structure, ignited and allowed to burn up all its fuel.

''The empty motor case will later be crushed and buried in an approved landfill within the grounds of the ammunition plant,'' the Pentagon said. ''Under the terms of the INF treaty, Soviet inspectors have the right to be present during the destruction process.''