WASHINGTON (AP) -- President Bush encouraged older and disabled Americans on Saturday to enroll in the prescription drug benefit that will soon be offered through Medicare."This new benefit is the greatest advance in health care for seniors and Americans with disabilities since the creation of Medicare 40 years ago," Bush said in his weekly radio address.Enrollment begins Tuesday and continues until May 15, 2006. The program itself begins January 1. To participate, people must enroll in a private plan that will cover a portion of their prescription drug costs.On average, the program will save beneficiaries about 50 percent on their prescription drugs, federal officials estimate. Beneficiaries who qualify for the low-income subsidy will save substantially more -- about 95 percent.Critics have described the program as much too complex, and recent surveys found potential beneficiaries wary. Nearly half of senior citizens don't believe the benefit will help them, according to a survey conducted last month by the Kaiser Family Foundation and the Harvard School of Public Health.Most beneficiaries will have more than 40 plans from which to choose, the government has said.Bush described the new benefit as a means of preventing serious illness. In the past, he said, Medicare would pay tens of thousands of dollars for ulcer surgery, but not a few hundred dollars for prescription drugs that would eliminate the cause of ulcers.The president stressed that the benefit is voluntary. He asked family and friends of senior citizens and the disabled to help with the enrollment process. They can call 1-800-Medicare for assistance."The sooner you enroll, the sooner you can have the peace of mind this coverage will bring," Bush said.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.