Response evaluation will be performed on day 22 (or 15 days after initiation of cytarabine and clofarabine) in the first course. One course of therapy will be for 28 days unless disease progression is seen. Participants may receive subsequent courses (up to 5 courses) if there is no disease progression or unacceptable toxicity. Sorafenib is given on days 1 to 7 and 15 to 28 in subsequent courses, and cytarabine with or without clofarabine will be administered starting on days 8 to 12 (clofarabine can be removed after course 2).