Seven weeks after the launch of the new federal health insurance marketplace, "30 to 40 percent" of the online system still has not been built or tested, including the critical component that processes tax credit payments to insurers, a top Obama administration official said today.

"Healthcare.gov, the online application, verification, determination, plan compare, getting enrolled, generating an enrollment transaction, that's 100 percent there," said Henry Chao, the Centers for Medicare and Medicaid Services project manager in charge of HealthCare.gov, told a House panel.

"There is the back office systems, the accounting systems, the payment systems. They still need to" be built, Chao said.

The Obama administration has said more than 100,000 Americans "selected health plans" through a state or federal insurance exchange in October, but it's unclear how many of those have made their first premium payment. Health insurers do not consider a consumer enrolled in a health plan until a first payment is received.

GOP Seizes on Obamacare Polls to Raise heat on Dems

Applicants' payments are processed directly with the insurance issuer, outside the marketplace, CMS officials clarified on a conference call with reporters. However, any government subsidy payment to the issuer would rely on the system in question.

"We do not need that online until about the middle of January given how the payment schedule works and we're on track to do that," CMS communications director Julie Bataille said on the call.

Chao told lawmakers that development of the "back end" of the website is continuing while the "front part" is operating and collecting consumer data.

"When we're trying to calculate a payment, derive a payment, do data matches on the back end, that doesn't affect the Healthcare.gov operations," he said.

Obama Tries a Pivot From Healthcare to Economic Growth

The first payment to the insurance companies will occur in early January, officials have said.

"We're focused on a troubled website that needs to be fixed. We're focused on solutions to problems that exist and rather than, you know, an ongoing political effort to undermine the Affordable Care Act without any alternative," White House spokesman Jay Carney told ABC's Jonathan Karl when asked whether President Obama was concerned about the situation.