JUNEAU — A judge on Friday rejected a request by state lawmakers to temporarily block Gov. Bill Walker from expanding Medicaid in Alaska.

Superior Court Judge Frank Pfiffner denied the request by the Alaska Legislative Council to bar Walker from implementing Medicaid expansion until the merits of the council’s case challenging Walker’s authority to expand Medicaid on his own are decided.

That means that unless the Alaska Supreme Court is asked to intervene and determines otherwise, Walker can move ahead with his plans to expand Medicaid next week, Pfiffner said.

The Legislative Council filed a petition Friday seeking a review by the Alaska Supreme Court, said Stacey Stone, an attorney representing the council.

In a statement, House Speaker Mike Chenault, R-Nikiski, said the lawmakers who supported the lawsuit “continue to feel very strongly about our constitutional argument that was presented. We are by no means looking for a way to stop Medicaid expansion; we are trying to do it the right way so that we have a reliable, sustainable system.”

Walker announced plans to accept federal funds to expand Medicaid coverage to thousands of lower-income Alaskans after state legislators tabled his expansion legislation for further review earlier this year. Walker has proposed rolling out the expansion on Tuesday.

Pfiffner’s ruling “ensures 20,000 working Alaskans will have access to health care on September 1st,” Walker said in a statement. State-commissioned estimates released earlier this year indicate that nearly 42,000 Alaskans would be eligible for coverage under expanded Medicaid the first year and about 20,000 would enroll.

The council, comprised of House and Senate legislators, voted 10-1 last week to sue Walker over his plans.

The argument in the case centers on whether the expansion population is a mandatory group for coverage under Medicaid or an optional group. The federal health care law expanded eligibility for Medicaid, but the U.S. Supreme Court in 2012 said states could not be penalized for not participating in expanding the program.

The lawsuit contends the expansion population is an optional group that cannot be covered unless such coverage is approved by the Legislature. The state Department of Law, representing Walker, argues that U.S. Supreme Court decision did not strike down the provision expanding eligibility but instead struck down the penalty for states that do not comply with it.

Pfiffner said that, at least in his preliminary view, the expansion population meets the language for required coverage.

He said he expected the parties would submit more detailed briefings from which he could make a final decision later on the merits of the case.

Under expansion, Medicaid coverage would be extended to people between the ages of 19 and 64 who are not caring for dependent children, not disabled and not pregnant, and who earn up to 138 percent of the federal poverty level. The federal government is to pay 100 percent of health-care costs for newly eligible recipients through 2016, stepping down to 90 percent by 2020.

Some legislators have expressed concern with adding more people to a system they consider broken. Administration officials have acknowledged the current Medicaid program isn’t sustainable, but they see expansion as a way to get federal dollars to help finance reform efforts.

Attorneys for the council argued the state could face irreparable fiscal injury if expanded Medicaid takes effect next week. They also said it could create an administrative nightmare if expanded coverage begins and is later determined unlawful.

In a court filing opposing the temporary restraining order, Department of Law attorneys said nothing would change with the scheduled Tuesday rollout of expansion that would harm the Legislative Council.

“All that will happen on that date is that some additional Alaskans will get federally funded health care coverage,” they wrote. If the court later decides that expansion is unlawful, it can halt expansion then and the coverage will stop, they wrote.

“The only ‘harm’ that will have occurred in the interim is that some indigent Alaskans will have received federally funded health care that they would not have otherwise received,” they wrote.