DISEASE CHARACTERISTICS: Histologically confirmed acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL) of B-cell or T-cell type, or blast crisis of chronic myelogenous leukemia (CML) Must fulfill one of the following criteria: - Newly diagnosed, previously untreated AML or ALL in elderly patients (65 75) - First or subsequent relapse of AML or ALL after standard chemotherapy, autologous or allogeneic bone marrow transplantation, or high-dose treatment with peripheral blood stem cell support - AML or ALL that is refractory to standard chemotherapy (no complete remission achieved after 2 courses of conventional induction chemotherapy) - CML in blast crisis of any subtype (i.e., myelogenous or lymphoblastic) with or without previously known chronic phase No leukemic involvement of the central nervous system