As House Democrats inch toward realizing their decades-long goal of providing health care coverage for nearly all Americans, emerging opposition from the Blue Dog Coalition is threatening that effort.

Three committees, Energy and Commerce, Ways and Means, and Education and Labor, had been expected to begin marking up a health reform package this week with a goal of moving the bill to the floor before the August recess.

But the bill’s hefty price tag — which could top $1 trillion over 10 years — and other concerns have stirred resistance from fiscally conservative Blue Dog Democrats and forced party leaders to delay introducing their legislation on Friday.

“There’s still some additional work that needs to be done,— Majority Leader Steny Hoyer (D-Md.) conceded late last week.

Democratic leaders have not yet said when they will release their health bill, and negotiations with the Blue Dogs are ongoing.

The delay comes after the Blue Dog Coalition sent a letter Thursday raising several concerns with the proposal that seeks to cover 95 percent of the nearly 50 million Americans who currently lack health insurance. They said the plan needs to make “significant progress— in providing more protections for small-business owners from being hit with insurance mandates, offering more health aid to rural areas and proposing additional cost-cutting.

Rep. Mike Ross (Ark.), who heads the Blue Dogs’ health care task force, warned leadership in a two-hour meeting Thursday night that his group of more than 50 Democrats would bolt unless a series of demands were met, including altering reimbursement rates under a proposed public insurance option so that they are not based on Medicare rates.

Ross and other Blue Dogs argue that the bill’s plan to base the public health insurance reimbursements on Medicare rates is unacceptable because it would undercut private insurers and thereby limit access to health care.

“We are losing doctors,— Ross said of his own hometown, which used to have six doctors and now has three. “We could give people a real shiny insurance card, but that’s not going to matter if they don’t have access.—

Another Blue Dog, Rep. Charlie Melancon (La.), said any health overhaul must not add to the federal deficit and should contain offsets for any new health care spending.

“Years of irresponsible governing and reckless deficit spending have left us in a deep hole,— Melancon said. “It is our responsibility as Members of Congress to meet these challenges head on, and that means passing fiscally responsible health care reform.—

Ross expects that some concerns could be addressed before the bill goes to markup and others could potentially be dealt with via amendments in committee. Melancon added that the Blue Dogs are committed to passing health care reform this year.

The Blue Dogs won’t find an ally in Energy and Commerce Chairman Henry Waxman (D-Calif.), a leading liberal, who last week declined to even set a cost goal for the legislation, saying instead the focus should be on providing health coverage. “The system is unsustainable, so something must be done,— he said.

Waxman downplayed pending scores on the cost of the legislation due from the Congressional Budget Office, saying solid estimates are “very difficult to pin down.— Additionally, Waxman has been a champion of a public health insurance option and has said the legislation will not pass without one being included.

Meanwhile, Rep. Michael Burgess (Texas), chairman of the GOP’s Congressional Health Care Caucus, said Republicans have been left out of negotiations and denied access to bill language. He said he will introduce a number of amendments during markup “in an attempt to improve the bill, but it’s hard to improve what you haven’t seen.—

GOP Members are expected to lambaste the cost of the proposal and make the case that it’s too expensive during turbulent economic times. While they’re unlikely to succeed in delaying the House bill, Republicans might find some bipartisan support for amendments that seek to find long-term savings in the health system.

Republicans will also challenge the need for a public health insurance option by arguing that it would eliminate private insurance plans. GOP Members may be unable to eliminate a public option completely, but they could find some Democratic support for setting a trigger that would allow a public plan to be accessed only if private insurance is not available.