WASHINGTON - Six Republican governors have agreed to expand Medicaid, the second-largest piece of President Obama's health-care overhaul, accepting federal money to ensure their state's residents have access to medical coverage.

Michigan Gov. Rick Snyder, an Affordable Care Act opponent, said Wednesday it makes sense for the "physical and fiscal health" of his state to participate in the law's expansion of Medicaid, the state-federal health plan for the poor. He became the sixth Republican governor to jump on board, following John Kasich of Ohio's announcement four days ago.

Snyder, Kasich and the rest of nation's 30 Republican governors generally oppose the $1.2 trillion health law as too costly. Five Republican governors have agreed to participate in the core provision of the law, building new marketplaces called exchanges to sell health insurance.

Kasich said while he remains opposed to the individual mandate and other provisions of the law, the Medicaid expansion is different. "This is not an endorsement of Obamacare," he said. "I think it's something to be considered separately from some people's strong feelings - including mine - about Obamacare."

Kasich's willingness to participate may help "break the logjam" among Republican governors opposing the Medicaid expansion, Ron Pollack, executive director of Families USA, said in a statement. Families USA is a Washington-based consumer advocacy group that supports the health-care overhaul.

Obama's health law, which passed Congress in 2010 without a single Republican vote, may extend insurance over the next decade to about 27 million people who are currently uninsured. The Congressional Budget Office estimates that 8 million more people will enroll in Medicaid programs next year because of the expansion.

Hospitals also have been pushing governors nationwide to participate in the expansion as they look to erase bad debt piled up from treating uninsured patients. In Michigan, Snyder said an expanded Medicaid program will cover 46 percent of the state's 450,000 uninsured adults and supplant the use of costly emergency rooms for primary care.

"Expansion will create more access to primary care providers, reduce the burden on hospitals and small businesses, and save precious tax dollars," Snyder said in a statement.

Republican governors in Arizona, Nevada, North Dakota and New Mexico have also agreed to participate in the Medicaid expansion, according to a tally by Advisory Board Co., a research and consulting company based in Washington. Including Democratic governors, 21 states will expand the number of people eligible for the health program.