"We're in a little different quadrants on this, the president and I. I do feel there needs to be some changes in the Medicare drug benefit in order to make it affordable," Budget Committee chairman Judd Gregg of New Hampshire said on ABC's "This Week."

New projections put the cost of the new drug benefit at $724 billion over 10 years when it starts in 2006, well above the original $400 billion estimate for the decade 2004-2013 the White House used in presenting the idea to Congress in 2003.

Some members of Congress have urged the law be changed to give the government the power to negotiate drug prices directly with pharmaceutical companies, a practice now prohibited. Others have renewed calls to let Americans buy less expensive drugs from Canada.

The congressional Republican leadership has generally opposed both drug importation and price negotiations.

Although the new estimates of its cost have sparked concern among many members of Congress, Senate Republican Leader Bill Frist said on "Fox News Sunday" there was no need to make changes now.

"I think we ought to let the program be implemented. It hasn't started. It's going to start in 2006. And then after a year, come back and see if we should make modifications," the Tennessee senator said.

The Bush administration considers the prescription drug benefit a milestone of the president's first term. The president said on Friday he would veto "any attempt to limit the choices of our seniors and to take away their prescription drug coverage under Medicare."

Bush was not aiming his veto threat at any specific proposals, his chief spokesman said. But the White House repeated its opposition to lifting the ban on price talks with drug companies.

The president has said he would try to bring Medicare finances under control after he finishes a push to make changes to the Social Security retirement program.

Gregg said the costs of the drug benefit needed to be in line with the original projections.

"There has to be spending restraint in that program. It was estimated to be a $400 billion program over ten years, that's what it should be," he said.