The Feb. 15 deadline is three months later than originally planned. The Obama administration extended the window in November to give states more time after Republican governors requested the department do so. States had until Dec. 14 to submit letters of intent, as well as detailed plans, to build their own state exchanges.

At the time U.S. Department of Health and Human Services Secretary Kathleen Sebelius said the administration is committed to "providing states with the flexibility, resources and time they need to deliver the benefits of the health care law to the American people."

Sebelius also said she believed states had sufficient enough time to decide their plans and told governors the administration looked forward to working with them on implementing the law.

A partnership agreement is just one of three exchange options for states. Exchanges can be run by individual states, by the federal government or by a combination of the two under an arrangement—the state partnership exchange.

The partnership model is an option provided to states that want to manage part of the exchange in 2014. HHS says it allows states to make key decisions and tailor the marketplace to local needs and market conditions.

Illinois joined Arkansas and Delaware in receiving tentative approval to operate a partnership exchange.

One state to watch today is New Hampshire, who announced this week it would seek to partner with the federal government to run their exchange fearing not doing so would lose control of how it would work. State law forbids New Hampshire from running its own exchange.

In addition to the three partnerships, 17 states and the District of Columbia have opted for running their own state exchanges, receiving conditional approval from the government.

The remaining states are expected to default to a federally operated state exchange.

Though the law intended that each state run its own exchange, many governors have refused to do so, and continually stalled plans. Others had complained there wasn't enough guidance from the government on how to do so.

All exchanges are required to begin open enrollment Oct. 1 and start coverage Jan. 1, the date that the law's individual mandate kicks in, requiring most Americans to buy health insurance. The exchanges set up under health reform are intended to give families and small-business owners "accurate information to make apples-to-apples comparisons of private insurance plans and, get financial help to make coverage more affordable if they're eligible."

[Also read: Feds begin marketing push for exchanges]