Medicare is “on-track for effective implementation” of the prescription drug benefit, Mark McClellan, administrator of the Centers for Medicare and Medicaid Services said Monday.

Despite recent criticism over the high cost of the drug benefit, McClellan said he was underscoring remarks by President Bush that the administration is “not going to back off our promise to seniors” for the benefit contained in the Medicare Prescription Drug, Improvement, and Modernization Act of 2003.

Bush said last week he would veto any bill that seeks to reduce the Medicare prescription drug benefit, which is scheduled to take effect in 2006.

Some Democrats said they plan to look at the Medicare law and make changes, despite Bush’s veto threat. Senator Majority Leader Bill Frist (R-TN) said the law should be implemented before changes are made.