The Bush administration yesterday tried to enlist the nation's governors as allies in its campaign to redefine Medicaid. But the governors said they would not embrace fundamental changes for the program unless they can learn more about the "fine print" than the president has disclosed -- and can design much of the plan themselves.

Rather than endorsing the administration's effort to give the states vast new control over the health insurance program for the poor, the National Governors Association assigned several of its members to draft a plan to change Medicaid, in part to alleviate financial strains the program is placing on state budgets.

Medicaid has been a dominant theme of the semiannual gathering of governors. That's because the program, covering 44 million poor and disabled Americans, is the largest contributor to historic budget deficits confronting states and because Bush is asking Congress to make the most profound changes in the program's 38-year history.

In essence, the president is offering states an approach that would temporarily help them with their financial predicament without actually providing additional money. States that chose to take part would gain an extra $12.7 billion for the next seven years, but their subsidies would be cut by the same amount for the three years after that. And for about one-third of the people on Medicaid -- those whom states are not required to insure under federal law but are covered anyway -- states would gain vast new freedom to restrict benefits, charge new fees, put people in private health plans, and subtract -- or add -- groups of patients.

At a White House meeting in the morning and a session with governors in the afternoon, Health and Human Services Secretary Tommy G. Thompson, a longtime Wisconsin governor before he joined the administration, lobbied his former colleagues unabashedly. "It is a very positive, a very progressive and a very innovative type of program that will benefit all of you," he said.

But governors of both parties, and two congressional Democrats with expertise in health care who addressed the governors, urged the administration not to press its plan without more input from the states and without explaining many critical details of the initiative.

New Mexico Gov. Bill Richardson (D) made what he called "a plea" to the administration and Congress to take the views of governors into account. He recalled that during his tenure as a House member, "my impression was, when governors came to speak to the Congress, almost nobody listened."

Richardson added, "I don't think his plan is, for my state, the answer," saying that states needed both more flexibility to run Medicaid and more money. In an interview over the weekend, he said Bush's plan would "let states take the heat. I don't see it as serious flexibility. It is flexibility to take people off the [Medicaid] rolls."

Connecticut Gov. John G. Rowland (R) praised Bush's approach, but said: "If we don't engage, if we don't make this our plan, it isn't going to happen. Instead of reading the fine print, we should be writing the fine print over the next weeks and months."

Governors traditionally have exerted strong influence over the nation's major social programs. In the 1990s, their support was instrumental in persuading Congress to overhaul the welfare system. Conversely, they were unable to reach consensus on proposals to convert Medicaid into a system of state-controlled block grants -- advanced two decades ago by the Reagan administration and again eight years ago by then-House Speaker Newt Gingrich (R-Ga.) -- and neither of those efforts prevailed.

Last week, Thompson told reporters that the governors' reaction during their four days of meetings that end today would be important in determining the fate of the new Medicaid plan.

Rep. John D. Dingell (D-Mich.) cautioned the governors that the administration has not issued any details of its proposal in writing. "We are essentially being compelled to quarrel about something that no one has seen," Dingell said.

The governors' group sent officials a list of 60 questions about the plan, addressing financial technicalities, medical services and eligibility rules, and how much of a burden the administration is willing to shoulder. It did not receive a reply.

Some governors, who had expressed skepticism over the weekend, said they were somewhat heartened after yesterday's meetings, in part, they said, because administration officials had answered a central question: Would the federal government continue the "entitlement" for Medicaid patients for whom states are required to provide coverage? The issue is crucial because it will affect whether states opting for the program's new version would be in a financially risky position if their caseloads increased more than their subsidies under the new funding method.

In the private morning meeting, governors said, Thompson assured them the federal government would continue to subsidize such patients, but then appeared to contradict that during the afternoon session.

Health and Human Services Secretary Tommy G. Thompson, right, talks with Sen. John Breaux (D-La.) before addressing a session of the National Governors Association.