MOSCOW (AP) _ A Soviet scientist said today the Kremlin could relatively cheaply and easily counter any deployment of President Reagan's proposed Strategic Defense Initiative.

Vitaly Goldansky reiterated at a news conference previous Soviet statements that Moscow could render Star Wars, as the space-based strategy is popularly known, ineffective.

He said ''diverse technology'' could be used ''to neutralize the anti- ballistic missile defenses.''

The physicist said this included existing weapons capable of destroying both stationary targets and warheads in flight, but did not otherwise elaborate.

The Soviets have maintained the U.S. plan, which Reagan has described as defensive, aims to give Washington the ability to attack from space. The Kremlin alleges the system is designed to provide first strike capability.