More than half of the state exchanges to be created under the 2010 U.S. health-care overhaul are expected to be run by the federal government, offering insurers and consumers uniform criteria in at least those areas.

While a final tally won't come until at least tomorrow, 32 states have either said they'll let the U.S. build all or most of their exchanges or are expected to, according to Avalere Health, a Washington-based consultant. That puts the onus on the Obama administration to set up and maintain the marketplaces that sit at the heart of the Affordable Care Act's mandate to expand medical coverage to as many as 30 million people.

The first six states to win U.S. approval for their exchange are split down the middle on what their programs will look like, with some requiring insurers to compete for access based on pricing and products. For the states likely to adopt the federal exchange plan, U.S. health officials have said any insurer can offer services if minimal standards are met.