WASHINGTON (AP) âÄî President Barack Obama wants a significant âÄúdown paymentâÄù for overhauling the health care system: $634 billion over 10 years. A senior administration official says ObamaâÄôs budget calls for financing the overhaul by trimming Medicare spending and limiting tax deductions for upper-income earners. The official spoke on condition of anonymity because the budget wonâÄôt be released until Thursday. About 48 million Americans are uninsured, according to recent estimates. The cost of guaranteeing coverage for all could easily exceed $1 trillion over 10 years. Obama has asked Congress for health reform this year, but senior members of both political parties say they are concerned about the cost.