Federal contractors have identified most of the main problems crippling President Obama’s online health insurance marketplace, but the administration has been slow to issue orders for fixing those flaws, and some contractors worry that the system may be weeks away from operating smoothly, people close to the project say.

Administration officials approached the contractors last week to see if they could perform the necessary repairs and reboot the system by Nov. 1. However, that goal struck many contractors as unrealistic, at least for major components of the system. Some specialists working on the project said the online system required such extensive repairs that it might not operate smoothly until after the Dec. 15 deadline for people to sign up for coverage starting in January, although that view is not universally shared.

In interviews, experts said the technological problems of the site went far beyond the roadblocks to creating accounts that continue to prevent legions of users from even registering. Indeed, several said, the login problems, though vexing to consumers, may be the easiest to solve. One specialist said that as many as five million lines of software code may need to be rewritten before the Web site runs properly.

“The account creation and registration problems are masking the problems that will happen later,” said one person involved in the repair effort.