In general, any bill that emerges from Congress is expected to follow Obama's blueprint for reining in health care costs overall while extending coverage to 50 million who lack it.

Another objective is to make sure that insurance companies can no longer deny coverage or raise premiums to unaffordable levels to individuals with pre-existing medical conditions.

But literally hundreds of details are involved in drafting legislation, and gaining a consensus even among Democrats is proving to be remarkably — if predictably — difficult, despite their large majorities in both houses.

As an example, some Democrats are demanding legislation that permits the government to sell insurance in competition with private companies. Republicans overwhelmingly oppose such a plan, deeming it a stalking horse for universal government-run insurance, and many Democrats have concerns, as well.

Some Democrats prefer a plan for a nonprofit cooperative to take the place of government in competing with private companies. Others favor a government role only in cases in which consumers lack a choice in coverage.

Similarly, Democrats are divided on paying for the bill, some preferring more tax increases than others, some favoring more cuts in Medicare and Medicaid.

"We've just got a lot of question and the top of the list would be how to pay for it," said Rep. Marion Berry, D-Ark., one of the Blue Dogs.

"I don't think we have significant cost-containment mechanisms in the proposal yet," said Rep. Adam Schiff, D-Calif. He said he favors provisions aimed at preventing overtreatment of patients and overpayments to doctors, hospitals and other providers.

A dispute over tax increases was at the core of upheaval in the Senate earlier in the week.

Sen. Max Baucus, D-Mont., and chairman of the Finance Committee, has been working for months with Republicans in hopes of gaining support for a bipartisan bill that can command 60 votes.

Efforts to raise money to pay for subsidizing the cost of insurance had focused on a tax on health care benefits for workers with high-cost coverage provided by their employers.

Baucus and Republican supporters argued it would also have tended to reduce the cost of health care overall, as well as offset the cost of the bill. But the Democratic leadership stepped in forcefully, citing poor public polling, opposition of organized labor and concerns about taxing middle-income workers.

As a result, Baucus and other members of the Finance Committee have broadened their search for alternative taxes to replace the $320 billion the benefits tax would have raised over a decade.

In addition to the tax on capital gains, officials said other options include a fee on insurance companies or drug manufacturers, a plan to allow states to issue health care bonds, and possibly a tax on sugary drinks.

An income tax surcharge on the wealthy was also on a list in circulation, as was Obama's proposal from last winter to limit the value of itemized deductions for those with the highest income.

Neither seemed likely to gain Republican support.