Lawmakers also wanted to know how many people have enrolled in plans through the health insurance marketplaces. Sebelius stuck with the administration response, promising to release the data in mid-November.
Starting Jan. 1, most Americans will be required to carry health insurance or face fines. At the same time, insurance companies will no longer be able to turn away people in poor health. The law provides subsidized private insurance for middle-class people who don't get health care on the job. Low-income people can access an expanded version of Medicaid in states that agree to expand that safety net program.
Congressional Republicans have introduced competing versions of legislation to let insurance companies continue selling coverage that has been available, freeing them from a requirement to cancel policies that do not meet the standards established in the law.
One bill in the House, authored by Rep. Fred Upton of Michigan, would cover the sale of policies providing individual coverage through 2014.
Republican officials said the House was likely to vote on the issue next month.
Sens. Ron Johnson of Wisconsin and Marco Rubio of Florida back Senate legislation that would apply to existing individual or group policies, and would permit their sale indefinitely. It was not clear if or when a vote might be held in the Democratic-controlled Senate.
Identical legislation has been introduced in the House by Rep. Ron DeSantis, R-Fla.