More than 447,000 of the poorest Ohioans could be eligible for federal government-funded health care coverage by the year 2020 under a Medicaid expansion plan endorsed Monday by Republican Gov. John Kasich.

The plan, part of the federal health care law, will keep $13 billion from going to other states, according to Kasich, who said the expansion will deliver services to the poor in a way that benefits all Ohioans.

Kasich opposed the health care law, known as Obamacare, but said he sees the Medicaid expansion differently. “Some of the poorest Ohioans, they get their primary care in an emergency room,” Kasich said. “When they go visit these emergency rooms and cannot pay, we all pay for it.”

The expansion of Medicaid, the publicly funded insurance program for the poor, would extend coverage to Ohioans earning up to 138 percent of poverty, or up to $15,415 a year for an individual. Ohio Medicaid currently covers 2.3 million poor and disabled people, an expense of $19 billion in state and federal money a year.

Maureen Corcoran, president of Vorys Health Care Advisors and a former state Medicaid official, said people with insurance pay about $1,000 a year to cover the costs of those who don’t have coverage. The expansion, she said, would shift some of those costs away from individual policyholders.

The U.S. Supreme Court upheld key aspects of the Patient Protection and Affordable Care Act last year, and made it optional for states to extend Medicaid. The expansion plan was included as part of the state budget and will have to be approved by the legislature.

Seventeen states and Washington, D.C., have agreed to expand Medicaid coverage under the Affordable Care Act. The federal government pledges to cover 100 percent of the cost of expansion for the first three years and then dial it back to 90 percent by 2020 and beyond.

If the feds change this deal, Ohio will reverse course, Kasich said.

The plan would expand the pool of eligible applicants beginning next year, reaching 366,000 by 2015 and 447,000 by 2020. However, state officials are bracing for what they are calling the “woodwork” effect. They estimate that roughly 231,000 people who are currently eligible but not signed up for Medicaid will enroll by 2015 when Obamacare’s individual insurance mandate prompts them to get coverage or face a fine.

Kasich said the expansion would recapture $13 billion in federal tax dollars over the next seven years — money he says would otherwise go to other states. The expansion will create a greater safety net for the poor and the mentally ill, he said, and ensure a healthier revenue stream to hospitals, which will have their reimbursements cut for uncompensated care under the ACA.

Officials with Columbus think tank The Buckeye Institute for Public Policy Solutions oppose the expansion and say it may result in higher taxes for Ohioans in the long run. But Dayton-based CareSource, Ohio’s largest Medicaid managed care plan, said the governor made the right choice.

“We all benefit from low-income Ohioans getting the health care coverage they need,” CareSource Chief Executive Officer Pamela Morris said in a statement.

Staff Writer Laura A. Bischoff and the Associated Press contributed to this report