WASHINGTON (CNN) -- House Democrats' push on health care legislation hit a snag Thursday when a group of fiscally conservative Democrats, known as "Blue Dogs," put on the brakes, pressing the Democratic leadership for significant changes to the draft bill.

Rep. Mike Ross, D-Arkansas, is a leading negotiator for the Blue Dog Coalition on health care.

As the Democratic leaders worked feverishly to finalize details of the legislation for a planned Friday rollout, the Blue Dog Coalition sent a letter late Thursday night saying the bill "lacks a number of elements essential to preserving what works and fixing what is broken."

Forty of the group's 52 members of the group signed the letter, making it clear that a major block of the House Democratic caucus wanted some concessions in order to get their votes. Shortly after the letter's release, a group of the Blue Dogs huddled in House Speaker Nancy Pelosi's office with other leaders for nearly two hours.

Arkansas Democratic Congressman Mike Ross, a leading negotiator for the Blue Dogs on health care, told reporters he, Rep. John Tanner, D-Tennessee, and Rep. Allen Boyd, D-Florida, also met with White House Chief of Staff Rahm Emanuel on Wednesday to go over their concerns.

"The message to him was the same as to the leadership -- that we could not support the current bill," Ross said.

Boyd told CNN that no deals were struck Thursday night, but that the group agreed to meet with House Energy and Commerce Chairman Henry Waxman, Ways and Means Chairman Charlie Rangel and Education and Labor Committee Chairman George Miller, on Friday. Boyd and other members representing rural areas pushed leaders to adjust the rates that rural doctors and hospitals are paid by Medicare for health care services.

"From a practical standpoint in terms of a timeline, a bill doesn't come into the House chamber until you got the votes to pass it, and I don't think they have the votes to pass it at this point. We've got to try to get to point where we're comfortable," Boyd said.

Pelosi repeated her pledge earlier Thursday that a government run health care plan would be included in the House bill. Ross said conservative Democrats have major reservations about how a public option would work. In the letter and in the meeting, the conservative Democrats stressed they did not want a "Medicare-like" structure for a public option.

"What we are saying is if there is a public option, it can't be based on Medicare rates unless the regional disparity in Medicare rates is fixed," said Ross, who also planned to press for more controls on government spending on healthcare and more savings from changes to Medicare.

House Majority Leader Steny Hoyer waved off any suggestions that the development Thursday night was a setback.

"Let me make it very clear that everybody in that room thinks we ought to pass health care," Hoyer said. But he also acknowledged that they still need to work through the details.



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