HARRISBURG - Simultaneous boos and cheers broke out among legislators in the House chamber on Tuesday when Gov. Corbett said he had no immediate plans to expand Medicaid eligibility for low-income Pennsylvanians under the federal Affordable Care Act.

The partisan reaction - among the strongest during his 45-minute budget speech - continued with instant news releases and social-media cheers and jeers, underscoring the political battle that still lingers concerning the federal health-care overhaul known as Obamacare.

Corbett won plaudits from fellow Republicans and criticism from Democrats for rejecting - at least for now - the addition of about 500,000 residents to Medicaid rolls, an option made available by the new law.

The governor said he had written to Kathleen Sebelius, secretary of health and human services, telling her that without flexibility, the costs to implement an expanded Medicaid program would be prohibitive.

"At this time, without serious reforms, it would be financially unsustainable for Pennsylvania taxpayers, and I cannot recommend a dramatic Medicaid expansion," Corbett said in his annual budget speech.

Republicans called the move fiscally responsible. Democrats denounced him for not taking the opportunity to provide insurance for low-income residents and passing up $12 billion in federal funds available in the first three years of the program.

"This would mean a half a million people would get insurance, it would take the burden off hospitals, and it would mean a largest injection of economic development dollars," said State Sen. Vincent Hughes (D., Phila.).

But House Majority Leader Mike Turzai (R., Allegheny) said expanding Medicaid eligibility now would surely lead to a tax hike later as federal subsidies decline, leaving the state to pick up a total of $4 billion by 2022, according to Corbett administration estimates. "We would have to raise taxes down the road," Turzai said.

A new report by the Henry J. Kaiser Family Foundation offered a less dire forecast, estimating Pennsylvania's costs for new Medicaid enrollees at $2.8 billion by 2022, while the federal government would provide $37.8 billion during that time period.

Corbett's announcement comes on the heels of a decision by one of his Republican counterparts, Ohio Gov. John Kasich, to opt into the Medicaid expansion plan, as Republican chief executives of three other states have done.

The wording of Corbett's speech appeared to leave open the possibility, though, that if the Obama administration were to build more flexibility into the program, Corbett might shift his stance.

Medicaid expansion was one of the hallmarks of the controversial health plan approved by Congress in 2011 and upheld last year by the U.S. Supreme Court. A total of 19 states and the District of Columbia have opted into the program. Enrollment for families of four earning up to $31,800 begins in October and money begins flowing to the states in January.

Under the expansion, the federal government covers 95 percent of the costs in the first three years, with the state's share increasing in future years.

Contact Amy Worden at 717-783-2584 or aworden@phillynews.com or follow @inkyamy on Twitter.