WASHINGTON--Secretary of State John Foster Dulles' doctors gave him a fighting chance Sunday to recover enough from cancer to stay on the job at least part time.

In private talks, the doctors were reported annoyed at some reaction to Dulles' new illness which already had counted him out of action at this critical juncture of world affairs.

They insisted it was too early yet for any worthwhile prognosis. They said medical science is far from powerless in dealing with cancer. Perhaps more importantly, they said no doctor ever would count out a man of Dulles' physical strength and will power.

The doctors have ruled out further surgery. Radiation therapy is scheduled to start this week. If that does not control the cancer, medical experts say a variety of other treatments could be tried--drugs derived from nitrogen mustard gas or perhaps injections of radiotive gold.

In many cases, doctors say, it is possible for the patient to return to work, especially in persons of advanced years. Dulles will be 71 on Feb. 25.

Western Europe sadly took it for granted Sunday that John Foster Dulles will have to bow out of the international arena.

Speculation about Dulles' successor centered on two men, Christian A. Herter and C. Douglas Dillon.

Segni Forms Cabinet

ROME--Antonio Segni, veteran Christian Democrat middle-roader, formed a one-party minority government Sunday that leaned a little to the right.

That was the opposite slant from the Christian Democratic Socialist government of Amintore Fanfani who resigned as premier Jan. 26 under fire from both wings of his shaky coalition.

The lean, 68-year-old law professor's Christian Democrats are 25 votes short of a majority in the Chamber of Deputies. They have 274 seats. Even with the support promised by the Liberals, with 17 seats, Segni would be eight votes shy. The Monarchists are split in two parties with a total of 25 votes.

Castro Named Minister

HAVANA--Fidel Castro talked over Cuba's most pressing problems Sunday with the ministers to be kept in the new Cabinet he will head as prime minister.

Castro hopes to speed up the government's economic, social and reform programs and reorganization of the government and army.

Two problems Castro is expected to deal with first are the reopening of the gambling casinos and the dispute over the right of asylum.

The asylum issue involves about 40 associates of ousted President Fulgencio Batista, the dictator who took refuge in Latin-American embassies in Havana when the Batista government fell Jan. 1.

Castro's government has refused safe conducts to those it considers refugees from justice. This has aroused opposition in the capitals of Latin America, where the right of asylum and safe conduct is traditional.