AUGUSTA, Ga., April 15--Cancer forced John Foster Dulles to resign today as Secretary of State.

The President said he had not made up his mind regarding a successor. He promised to fill the post "as quickly as practicable." Reports continued that Undersecretary Christian A. Herter is the most likely choice.

Eisenhower said that Herter--even if he does not become Secretary--will be on hand when the Western ministers meet with the Soviet minister at Geneva May 11.

Meanwhile, at Washington's Walter Reed Army Hospital, where Dulles is undergoing treatment for cancer, officials said the Secretary's condition remained unchanged.

Red China to Communize Tibet

TOKYO, April 15--Red China made clear today it plans to start communizing Tibet soon. "Tibet is not an independent state," said the official Peiping People's Daily.

The Reds' proposals for communizing Tibet probably will be announced at the Chinese people's congress Friday. But the Panchen Lama, the Communists' puppet ruler, apparently gave his approval in advance.

Castro Arrives in U.S.

WASHINGTON, April 15--Prime Minister Fidel Castro arrived here tonight to begin a 10-day speaking tour of the United States. A crowd of approximately 200 Dominican exiles and Cuban supporters held aloft flags and cheered his arrival.

U.S. Space Program Criticized

WASHINGTON, April 15--Vice Adm. John T. Hayward testified today that the nation's space program is cumbersome and certain to run into serious delays.

He urged that the separate civilian and military space agencies be brought under a single over-all unit similar to the Atomic Energy Commission. Hayward, boss of the Navy's research and development programs, testified before the Senate Space subcommittee.