WASHINGTON - Senate Democratic liberals are seeking expansion of two large federal programs, Medicare and Medicaid, in exchange for dropping a government-sold insurance option from health-care legislation sought by President Obama, several lawmakers said yesterday.

Under the potential trade-off with party moderates, near-retirees beginning at age 55 or 60 who lack affordable insurance would be permitted to buy coverage under Medicare, which generally provides medical care starting at 65. Medicaid, the federal-state health-care program for the poor, would be open to all comers under 150 percent of poverty, or slightly over $33,000 for a family of four.

Senators and aides said the changes had been discussed extensively in recent days as a small group of moderate and liberal Democrats seek a middle ground on the bill.

Given the complexities of the two programs, and the White House goal of passing legislation by year's end, it wasn't clear whether the negotiations would ultimately prove successful, or merely were a last stab by liberals to salvage some concession in a months-long debate.

Senate Majority Leader Harry Reid (D., Nev.) imposed a deadline of today to complete the talks, said Sen. Tom Harkin (D., Iowa), a participant in the negotiations.

"It's one of those kind of things in the middle that doesn't make everybody very happy, but that's our compromise," Harkin said.

As the search for compromise intensifies, several Democrats said a plan by Sen. Maria Cantwell of Washington was drawing new interest. It would give states an option to negotiate with private industry to provide group coverage for lower-income residents. The bill now allows that for any state's residents up to twice the federal poverty level, about $44,000 for a family of four, but that could be raised if negotiators decide they want to do so.

Finance Committee Chairman Max Baucus (D., Mont.) said, "It's probably the closest proposal thus far that could get the support of 60 senators. It's got legs."

Democrats need 60 votes to pass their bill over Republican objections, and while liberals far outnumber moderates in the party, they appear at least four votes short of the number needed. That gives moderate Democrats such as Sens. Blanche Lincoln of Arkansas, Mary Landrieu of Louisiana, and Ben Nelson of Nebraska plus Joe Lieberman (I., Conn.) leverage as the White House and Reid try to complete work on the bill.

At its core, the legislation is designed to expand coverage to more than 30 million who lack it, while curbing controversial industry practices and generally restraining the growth of medical spending.

The closed-door talks have proceeded while Republicans on the Senate floor have mounted politically charged challenges to the health-care bill. So far they have failed to win any major changes.

Yesterday, the Senate rejected, 43-56, an attempt by Sen. Judd Gregg (R., N.H.) to prevent Medicare from "being raided" to pay for health care. The bill calls for cuts totaling $460 billion over a decade from projected Medicare spending, much of it to be used to provide subsidies to help lower- and middle-income Americans buy health care.

Another contentious issue is slated for a vote today, when conservatives from both parties try to strengthen abortion restrictions in the legislation.

As drafted, the bill requires insurers to offer policies that both provide and lack abortion coverage in any state where they offer coverage under a new marketplace through which consumers would shop for government-regulated insurance policies.

Any consumer who receives federal subsidies to defray the cost of insurance would have to use personal funds to pay for abortions, except in cases of rape or incest or if the mother's life is in jeopardy.

Senators led by Nelson, Orrin G. Hatch (R., Utah), and Bob Casey (D., Pa.) want to ban any insurance plan from providing most abortions if any of its policyholders receive a federal subsidy, a stronger restriction that is more in line with provisions in the House-passed bill.

While the proposed change enjoys bipartisan support, it is unlikely to command the 60 votes needed to prevail.

It was unclear whether abortion opponents would try again if their first effort fails, or whether the issue would be laid aside until any House-Senate negotiations on a compromise.