WASHINGTON – President Bush added Medicare to the government’s fix-it list yesterday after new figures showed the first full decade of the program’s prescription benefit will cost taxpayers $724 billion.

“There’s no question that there is an unfunded liability inherent in Medicare that Congress and the administration is going to have to deal with over time,” Mr. Bush told reporters.

“Obviously I’ve chosen to deal with Social Security first,” he added. “Once we modernize and save Social Security for a young generation of Americans, then it’ll be time to deal with the unfunded liabilities of Medicare.”

The new figure for years 2006 through 2015 is much higher than the $534 billion cost calculated for years 2004 through 2013. That’s because under the previous decade-long projection, the benefit didn’t exist for two of the 10 years. Congress passed the prescription drug benefit at the end of 2003, but except for some low-income seniors, it delayed making it available until January 2006. Nonetheless, several lawmakers said yesterday that they had been deceived on the program’s true cost.

“This new information further demonstrates what appears to be an attempt to dupe Congress and win passage of the legislation,” said one such lawmaker, Senator Feinstein, a Democrat of California, calling for an investigation by the Senate Finance Committee.

Some Republicans long skeptical of the administration’s estimates also expressed alarm at the escalating costs as more people reach age 65 and qualify for it and drug prices continue to rise.

“I do think we are going to have to go back and readdress it,” said Senate Budget Committee Chairman Judd Gregg, a Republican of New Hampshire.

Congress narrowly approved the drug legislation in 2003 after an all-night debate. The administration told wavering lawmakers that the program would cost $400 billion, including expected savings. The White House revised the estimate to $534 billion just two months later, after the law was enacted.

The $724 billion figure is in documents obtained yesterday and related to the president’s Monday budget request to Congress. Without anticipated savings included in the calculation, the cost of the program over the next decade could swell to $1.19 trillion, ac cording to the documents.

White House Budget Director Joshua Bolten said the new price tag of $724 million reflects $134 billion in savings the government expects because states are paying some drug costs, $145 billion more from beneficiaries’ premiums and $200 billion in savings by switching some Medicaid prescription benefits to Medicare.

Under the program:

* Participants must pay monthly premiums that are expected to average $35 in 2006.
* The participants must pay out of their pockets the first $250 in pharmacy bills.
* Medicare will then pick up 75% of the next $2,000 in prescription expenses.
* Then a gap is built into coverage, during which participants must pay all drug costs until the total tops $5,100.
* The government will then pay 95% of prescription bills above $5,100 a year.

In a budget-related development yesterday, a liberal think tank report said spending restraints in Mr. Bush’s budget proposal would mean deep cuts to environmental protection, community development, and veterans benefits through the end of the decade.

The Center on Budget and Policy Priorities said its calculations, made using budget information provided to congressional committees, reveal future spending cuts that the White House wants but didn’t detail in the 2006 budget. By proposing annual lids on government spending without giving program-by-program details of potential program cuts in 2007 through 2010, the report said, the White House sidestepped a debate on policy trade-offs. “It is difficult to assess the impact of the proposed caps when one does not know what types of cuts the administration is planning to achieve them,” the report concluded.

White House budget office spokesman Chad Kolton would not comment specifically on the center’s calculations, but said future budget decisions will be made year-by-year.

“There is still ample room for increases in priority programs,” he said. “We’re happy to talk about what we can do going forward, even in very restrained budgets.”