From Wire Dispatches

In what may have been the heaviest death toll on a U. S. installation in the war, 33 Americans are dead and 76 wounded after a Viet Cong attack Sunday on Fire Base Mary Ann, an artillery base 50 miles south of Da Nang.

The casualties are expected to go still higher on the basis of incomplete reports from the U. S. Command. Communications with the base were spotty more than 24 hours after the North Vietnams attack, apparently because of damage to the control bunker.

In another development in Southeast Asia, a U. S.-supported South Vietnamese raid on a major North Vietnamese headquarters inside Laos was canceled because of heavy anti-aircraft fire and fog.

The strike was approved by President Nixon and President Thieu of South Vietnam but was called off when intensive B-52 air strikes failed to silence North Vietnamese anti-aircraft fire.