The federal government would initially pay 100 percent of the additional costs, which would then drop slightly. But Deal said the long-term costs would be too severe.
"I think it is probably unrealistic to expect that promise to be fulfilled in the long term, simply because of the financial status that the federal government is in," he said, according to the Journal-Constitution.
Roughly 650,000 people in Georgia would have gotten coverage from the expansion, the paper reported.
A handful of GOP governors have said they won't take part in the Medicaid expansion, largely out of staunch political opposition to the health law. Deal, though, has been somewhat less unbending than other Republicans about whether to implement the other big piece of the law — a state-based insurance exchange.
Deal established a committee to study the state's options for an exchange, and he has acknowledged, at least rhetorically, that a decision not to create a state-based exchange would invite a greater federal role in healthcare.