Ky Threatens to Invade N. Vietnam

South Vietnam's Vice-President Nguyen Cao Ky said yesterday an invasion of North Vietnam would be necessary to prevent another Dien Bien Phu.

In South Vietnam, rumors persisted that U. S. ground troops had crossed into Laos, despite repeated denials by American officials.

Warning

Ky warned that South Vietnamese forces in Laos could be destroyed unless the North Vietnamese are cut off from their bases. To do this, Ky said, South Vietnamese troops would cross the Ben Hai River into North Vietnam. The river is the dividing line at the 17th parallel between North and South Vietnam.

Senior American Defense Department officials in Washington yesterday defended Ky's statement, They said Hanoi may be deterred from sending reinforcements to Laos because of fear that the South Vietnamese may invade North Vietnam.

It was learned late last night that a special landing force of 1500 U. S. Marines was rushed to the northern coast of South Vietnam to counter a possible North Vietnamese drive across the Demilitarized Zone.

Americans in Laos

American soldiers at Khe Sanh told UPI correspondent Kenneth Braddick that at least 100 American ground troops had entered Laos during the past 3 days and fought against Communist troops there. The U. S. troops were allegedly flown into Laos by American helicopters.

The soldiers, members of the 3rd Platoon, Delta troop, 7th Battalion, 17th Air Calvary, declined to use their names because they feared disciplinary action by their superiors.

U. S. spokesmen in Saigou denied that U. S. troops were involved in Laos, but did admit there was considerable latitude on steps which may be taken to rescue downed American helicopter crews in Laos.

Reconaissance

U. S. military sources in Saigon also confirmed reports that Americans are involved in clandestine reconnaissance activities in the Ho Chi Minh supply complex in Laos, and that these activities have been going on for at least 5 years.

Plea for Reinforcements

Dispatches from Vientiance reported intensified Communist pressure against Long Chen, the center of U. S. Central Intelligence activities in Laos. Gen, Vang Pao, leader of the CIA-supported Meo tribesmen, flew to Vientiane to plead for reinforcements and more U. S. tactical air support.

In other developments, South Vietnamese forces drove 25 miles inside southern Laos yesterday and seized Sepone, reported to be a major communist supply center, South Vietnamese engineers are rebuilding the town's abandoned airstrip, which will allow them to fly reinforcements and supplies into southern Laos.

Heart Attack

In Pnomh Penh, Gen. Lon Nol was reported in fair condition after suffering a heart attack Tuesday. One half of his body is reportedly paralyzed, and he will be inactive for at least one month.

Meanwhile. Secretary of State William P. Rogers announced in Washington yesterday that U. S. troops remaining in Vietnam after May 1 will not go into combat.

Rogers' statement-prompted by word from the White House that only 40,000 to 50,000 of the U. S. troops in Vietnam will remain in the combat zone after that date-appears to be consistent with the current American strategy of Vietnamization and increased air war.

Asian Conference

In the Senate, Sen, George D. Aiken (R-Ver.) urged the nations of Southeast Asia to convene their own international conference, in Asia, to settle the war in Indochina. Stating that peace "cannot be imposed by others," Aiken suggested that such a conference should include Japan, Communist China, and the Soviet Union. "I cannot believe that Russia has of late bad a vested interest in keeping up the conflict in Indochina," he said.