Final negotiations on merging the bills began in earnest Wednesday as congressional leaders spent more than eight hours behind closed doors at the White House using a process that bypasses a formal conference committee and cuts out Republican participation.

They dug into a series of sticky issues that separate the two versions of the bill passed by the House and the Senate — including abortion, access to health insurance by illegal immigrants, and how to pay for the sweeping legislation, which will insure an estimated 37 million Americans over the next decade.

A White House statement said they had made “significant progress in bridging the remaining gaps” between the bills.

Republicans have been howling about the process for nearly two weeks — House Minority Leader John Boehner, R-Ohio, called it “a breeding ground for more of the kickbacks” — but now congressional leaders are facing a growing mutiny within their own ranks.

Wednesday, Sen. Mark Udall, D-Colo., suggested the talks lacked transparency and called for televising final negotiations. Sen. Michael Bennet, D-Colo., also said final talks should be open to live cameras.

“I haven’t been in Washington long, but one thing I can tell you is this is one town that can use some fresh air, and some real transparency,” Bennet said. “The outcomes from the negotiations on the health care reform bill are far too important to be done behind closed doors.”

Those criticisms could create significant difficulties for efforts to finish the health care bill and move on to other legislation before the press of this year’s election cycle swamps Congress.

Media organizations and others have said televising final negotiations between the House and the Senate would be natural given the enormous potential impact of the legislation.

Instead, Democrats have created a process under which House and Senate leaders will hammer out key compromises, then send the retooled bill to both chambers.

Those negotiations are expected to go for days, if not weeks, and Democratic leaders have said a conference would only provide Republicans — only one of whom voted for the bills in either chamber — a new chance at obstruction.

“This non-conference conference was a bid to speed this up and bring it to an end. A conference committee seemed one more area where Republicans would attack the Democrats and liberals would get upset with leadership,” said Julian Zelizer, an expert on Congress at Princeton University.

“The problem is it looked bad. Republicans can use that to say health care is being rushed through and done behind closed door because Democrats want to hide something,” he said. “That’s why you’re seeing Democrats now getting nervous about the process as well.”

Fellow Republican, Sen. Bob Corker, said the bill is “fundamentally flawed” and called for bipartisanship.

The bill, approved on a 60-39 vote, must still be merged with legislation passed by the House.

“The Senate health bill will prove to be an historic mistake if this or anything like it is ultimately signed by the president,” said Alexander, who is chairman of the Senate Republican Conference.

“Congress set out to reduce health care costs to Americans and Democrats have managed to do the exact opposite. Their written-in-secret bill will increase health insurance premiums, raise taxes, cut Medicare and dump millions of Americans into Medicaid.

“For Tennessee, Medicaid’s expansion and the bill’s ‘sweetheart deals’ would cost our state more than $750 million over five years when fully implemented, forcing tax increases or damaging higher education—or both.

“Instead, we should start over and move step-by-step to reduce health care costs using the steps that Republicans have repeatedly proposed: let small businesses pool resources for health insurance; allow purchasing of health insurance across state lines; end junk lawsuits against doctors; eliminate waste, fraud, and abuse; expand health savings accounts; and promote wellness and prevention.”

Corker said in his statement, “I’ve spent almost three years and countless hours in bipartisan meetings working toward reforms that would enable all Americans to access affordable, private health insurance.

“I wanted a bipartisan health care reform bill that would stand the test of time. Instead, we were forced to vote on a 2,000-plus page, fundamentally flawed, partisan bill that expands Medicaid by sending $25 billion in unfunded mandates to states, takes $464 billion away from Medicare and leverages it to create a new entitlement, uses budget gimmickry to hide its true cost; increases federal costs, and actually causes Americans to face increased taxes and premiums.

“It’s my sincere hope that Congress returns in 2010 more willing to work in a bipartisan fashion, and my work on financial regulatory reform gives me hope that that’s possible.”