But how much consumers will have to pay for insurance — perhaps the greatest factor in whether young and healthy people sign up — won’t be announced in many states until September. Sebelius said the administration is negotiating with insurers now on rates in the states where the federal government will run the exchange. It’s a more active role than the administration first suggested it would play in rate-setting.

“What consumers should be confident about is we intend to do rate negotiation and make sure that the plans offer consumers the best possible choices,” Sebelius said.

The Congressional Budget Office has estimated that 24 million people will get health insurance on the exchange by 2023, but only 7 million in the first year. Millions more can go into expanded Medicaid, although those projections were cut after the Supreme Court last year allowed states to opt out.

Sebelius on Monday said 7 million is a “realistic target.”

“We’re going to be driving our efforts toward that kind of enrollment effort,” she said. “It’s both about numbers and also hopefully getting a balanced risk pool.”