A crucial medicine to treat childhood leukemia is in such short supply that hospitals across the country may exhaust their stores within the next two weeks, leaving hundreds and perhaps thousands of children at risk of dying from a largely curable disease, federal officials and cancer doctors say.

"This is dire," said Valerie Jensen, associate director of the Food and Drug Administration's (FDA) drug-shortages program.

Methotrexate is the drug, and among the cancers it treats is acute lymphoblastic leukemia, or ALL, which most often strikes children between 2 and 5 years of age. It is an unusually virulent cancer of white blood cells that are overproduced in bone marrow and invade other parts of the body.

The cancer commonly spreads to the lining of the spine and brain, and oncologists prevent this by injecting large quantities of preservative-free methotrexate into the spinal fluid. The preservative can cause paralysis when injected into the spinal column, so cannot be used for this disease.

Methotrexate is also used to treat rheumatoid arthritis, other cancers and severe psoriasis, among other diseases.

Ben Venue Laboratories was one of the nation's largest suppliers of injectable preservative-free methotrexate, but the company voluntary suspended operations at its plant in Bedford, Ohio, in November because of "significant manufacturing and quality concerns."

Since then, supplies of methotrexate have gradually dwindled to where oncologists say they fear shortfalls may occur at many hospitals within two weeks.

"This is a crisis that I hope the FDA's hard work can help to avert," said Dr. Michael Link, president of the American Society of Clinical Oncology. "We have worked very hard to take what was an incurable disease and make it curable for 90 percent of the cases. But if we can't get this drug anymore, that sets us back decades."

There are four other methotrexate manufacturers in the United States, and they are trying to increase production, Jensen said. The FDA is also seeking a foreign supplier, she said.

This year, at least 180 drugs crucial for treating childhood leukemia, breast and colon cancer and other diseases have been declared in short supply, a record number.