Five months after arriving in the United States, the popular Czechoslovak ambassador, Rita Klimova, has been diagnosed as having the early stages of malignant leukemia. She is torn about whether to stay in Washington or return home.

Klimova, who has no medical insurance, said in an interview yesterday that her decision is a financial one and depends on her ability to find treatment that "fits into someone's research plans."

"My government will pay," said Klimova, 58. "I'm entitled. But the financial aspect is worrisome, and I have a bad feeling about running up a big bill for my country."

The lively, outspoken Klimova, whose New York accent is traceable to her family's life in Washington Heights during the Nazi occupation of Czechoslovakia, initially became ill in early May while attending a conference in Israel with Czechoslovak President Vaclav Havel. Her leukemia diagnosis, however, is a recent one.

When she returned to Washington from Israel with flulike symptoms -- a high fever, a cough and head congestion -- doctors could not determine the cause of her illness, calling it a fever of unidentified origin, and even starting treatment for possible tuberculosis.

Then last month, during her second stay in Arlington Hospital, she was visited by President Bush's physician, Burton Lee, who arranged for her to be admitted to a VIP suite at the Walter Reed Army Medical Center. "Theoretically, I should have gone home immediately because of the hospital bills" from Arlington Hospital, said Klimova, who arrived as ambassador on Feb. 12. "I was grateful that the decision-making was taken off my shoulders."

Doctors at Walter Reed diagnosed "smoldering leukemia" and a severe sinus condition, which they treated by cleaning her sinuses surgically and with antibiotics, which she is still taking. Because of her concern about its cost, however, Klimova has not begun any treatment for the leukemia.

Although she continues to fulfill her ambassadorial duties -- yesterday afternoon she headed to Capitol Hill to try to persuade some members of Congress that Czechoslovakia deserves a most-favored nation status -- she admitted that her illness has made it difficult to maintain a balance between her personal and professional life.

She gets to her office each morning now at 9 rather than 8, sometimes takes a nap in the afternoon, and has stopped traveling. She is even a little worried that she might have to renege on a speech in Colorado at the beginning of next month if she begins chemotherapy.

According to the ambassador, a former economist who was visible in the early days of the Czechoslovak revolution last year as President Havel's first translator, there has been no pressure from her children or her government to return.

"I feel better every day, and my minister doesn't want me to resign," she said, referring to Czechoslovak Foreign Minister Jiri Dienstbier. "He says I can do my work by telephone from the hospital. And friends and doctors have said my chance of survival is better in the U.S.

"It's not that we don't have good doctors at home," she explained. "But we don't have the ability to protect patients from infection. That requires a high degree of sophistication in the hospitals."

Her recovery also requires drugs, which she supposes she could bring from the United States, and an appropriate diet, which is more problematic. "All the orange juice I've drunk here... .," she marveled. "Orange juice is only available in the winter in Prague and then somebody has to squeeze it."

Before she became ill, Klimova had had the normal series of medical ups and downs: appendicitis, a hysterectomy, "a headache here, a backache there -- like ladies who are 58," she said. The leukemia is her first major setback.

She is surprisingly sanguine, however, about developing a life-threatening illness just as her country embarks on a new life. "We have a saying in Prague," she said. " 'No one's trees go to the sky.' And I've lived to see lots of things I never thought I'd see -- Czechoslovakia without communism. I've done things I always wanted to do -- last week I took my son to New York to see the neighborhood where I grew up."

Reflecting for a moment, Klimova said, "You know, I visited the U.S. in 1988 for the first time since I lived here as a child. I wanted to come again and had half an invitation to return to teach.

"But to return as ambassador, what more could I want?"