"Despite repeated claims that illegal aliens will not benefit under any health care reform bill, language passed by the House ... does not require sufficient proof of identity and U.S. citizenship status as a condition for being determined eligible for benefits provided under the legislation," Deal wrote the senators.

Isakson’s press secretary, Sheridan Watson, responded to a request for comment from The Times with a statement that both the state’s senators "are committed to ensuring that illegal immigrants will not be eligible for benefits under any health care plan passed by the Senate."

The Senate version of the bill is estimated to extend coverage to 94 percent of eligible Americans at a cost of $849 billion. Initial maneuvering on the Senate floor was expected later in the week on the measure, bitterly opposed by Republicans eager to deny President Barack Obama a victory on his top domestic priority.

Officials have said the measure would require most Americans to carry health insurance and would mandate large companies to provide coverage to their workers, as well as ban insurance company practices such as denying coverage on the basis of pre-existing medical conditions.

As rank-and-file Democrats gathered to learn details of the measure, a senior Democratic leadership aide said the Congressional Budget Office had estimated it would spread coverage to 31 million Americans who currently lack it while still reducing federal deficits by a total of $127 billion over 10 years.

The aide also cited a CBO estimate that the bill would achieve cuts of $1 trillion over a decade in projected health care costs. The estimate of 94 percent coverage was less than the 96 percent estimated for legislation the House passed earlier this month, but no precise comparisons were possible without as-yet-unreleased CBO documentation.

The aide spoke on condition of anonymity, saying rank-and-file senators had not yet learned of the details.

Aides have said previously much of the bill would be financed by cuts in projected Medicare payments. Reid has also had under consideration higher payroll taxes for upper wage earners, but there was no word on whether he had decided to incorporate that provision into the measure he crafted.

At its core, the bill would set up new insurance marketplaces — called exchanges — primarily for those who now have a hard time getting or keeping coverage. Subsidies would be available to help defray the cost of coverage for people with lower incomes.

Reid announced two weeks ago it would also include an option for consumers to purchase government-sold insurance, with states permitted to drop out of the system.

Reid did not speak with reporters before stepping into the closed-door caucus, although he was expected at a news conference later in the evening.

In a sign of the challenge confronting him, the Nevada Democrat met earlier in the day with Sens. Ben Nelson of Nebraska, Mary Landrieu of Louisiana and Blanche Lincoln of Arkansas, moderates within his party who have expressed reservations about the bill.

"He is walking through the particulars with them," said Reid’s spokesman, Jim Manley. "We need 60 votes to get this bill to the floor."

Nelson later issued a statement strongly suggesting he would vote with fellow Democrats on an initial showdown expected within days. Landrieu said, "I’m not going to be for anything that doesn’t drive down costs over time."

Lincoln, the only one of the three who faces re-election next year, told reporters, "We’ll wait and see."

With the support of two independents, Democrats have 60 seats, the precise number needed to choke off any Republican delaying tactics. None of the 40 Republicans is expected to defect on the first test vote, expected by weekend.

Reid was releasing his legislation more than a week after the House approved its version of the health care bill on a near party-line vote of 220-215.

According to estimates from the Congressional Budget Office, that House bill, with a price tag of about $1.2 trillion, would result in coverage for tens of millions of uninsured, and provide 96 percent of the eligible population with insurance.

Two Senate committees approved different versions of a health care bill earlier in the year, and while Reid has said he would produce a blend of the two proposals, in fact he had a virtual free hand to come up with a plan that could command the 60 votes needed to pass.

Anticipating a major struggle, the White House deputized Interior Secretary Ken Salazar and former Senate Majority Leader Tom Daschle to join Vice President Joe Biden in trying to clear the way for the bill’s approval over the next several weeks.