The White House has been secretly drafting its own health care legislation that it may unveil at some point during the debate if officials believe it would help secure passage of a bill, according to sources familiar with the effort.

Sources differed on how far the process has gotten, with some saying a bill is basically finished and others saying they are aware only of a partially completed effort. White House officials, though they know their preferences, also appear to be constructing different options that could be thrown together depending on how the legislation is shaping up in Congress.

But all sources knowledgeable about the effort agreed the measure includes significant detail and possibly even some legislative language that could ensure the bill is ready to go the moment it is needed.

“They are getting ready for a backup,— said one veteran observer of health care debates who was knowledgeable about the effort. “It will be parachuted in if necessary.—

The White House measure appears designed to entice moderate Democrats and perhaps even Republicans into supporting a health care overhaul if legislative efforts in Congress fail or if they move too far to the left. Sources said one possibility would be to invoke the measure if the Senate cannot rally 60 votes to break a filibuster. Another option may be to present details of what the White House wants during a conference between the House and the Senate.

But the White House effort may never see the light of day.

At the moment, the Senate Finance Committee is moving legislation that includes many provisions and a price tag supported by President Barack Obama, and the need for a White House bill may now be moot. One of the reasons for embarking on the project was to have a detailed proposal ready in case the Finance Committee failed to move a bill that could pass the Senate.

[IMGCAP(1)]The White House effort has been held close to the vest and sources were not aware of the details of the plan. White House aides did not respond to numerous requests for comment.

One lobbyist working the health care beat — who was not aware of the White House plan — was not surprised at the White House’s reluctance to talk, saying moderates would demand details and liberals would be concerned the White House was selling them out.

The existence of White House proposals helps explain Obama’s specificity during his Sept. 9 health care address to Congress in naming a 10-year $900 billion price tag for “the plan I’m proposing.— During his remarks, Obama gave no details about how he arrived at the number. But Obama aides had by then worked out their preferences in enough detail that they were able to run the numbers.

Some on Capitol Hill have felt frustrated that the White House put out a number but failed to provide a road map for getting there. But others are content to have the White House stay out of the fray and let lawmakers take the lead.

The failure to share details of what the White House wants fits with a strategy that aims to allow lawmakers leeway in crafting a bill. The strategy appears deeply informed by the failure of President Bill Clinton in 1994 to get Congress to act on health care.

Several administration officials and advisers are veterans of the Clinton effort, which featured a detailed White House proposal that became a magnet for criticism from opponents. Some believe the effort by the White House to steer the debate is what led to failure.