The pace of Americans signing up for privately administered insurance through President Obama's health care law slowed down in February, according to a new report from the Department of Health and Human Services, and youth enrollment is well below target levels set before the program's launch.

Weeks before the health care law's exchanges launched Oct. 1, an HHS memo projected that 5.7 million individuals would enroll in a plan through one of Obamacare's exchanges by the end of February. In reality, HHS said Tuesday, just 4.2 million Americans had signed up in the first five months.

HHS still hasn’t disclosed how many Americans who have signed up for a plan through the website have consistently paid their premiums, which is how enrollment is typically measured. Thus, HHS figures could overstate enrollment by around 20 percent to 25 percent.

With the open enrollment period set to expire at the end of March, the pace of signups is slowing down.

In January, 1,146,071 individuals signed up for insurance on the exchanges, according to HHS. In February, that number declined to 942,800.

That difference cannot be explained away merely because there are fewer days in the month in February. Originally, HHS projected that 212,000 more Americans were going to enroll in a health care plan in February than January, the belief being that enrollment would accelerate over time.

The slower pace of signups is potentially worrisome for the health care law, as the administration needs to build momentum in the final weeks of open enrollment, which ends March 31.

Further worrisome for backers of the law is that young people still aren’t signing up in the numbers the administration once deemed necessary for the program’s viability.

The White House had originally said nearly 40 percent of the 7 million Americans initially projected to enroll would have to be young and healthy to offset the cost of covering older and sicker Americans. When initial signs pointed to low youth enrollment, many supporters of the law argued that younger individuals would enroll later in the process.

But in February, individuals between 18 and 34 years old made up just 27 percent of those signing up — the same as January. Cumulatively, just 25 percent of signups have come from that age demographic.

This makes it highly unlikely that the administration will meet enrollment goals. If March enrollment roughly doubles from February, and the exchanges end up with 6 million signups, roughly two-thirds of March enrollments would have to be from the 18-34 age group to achieve the target demographic mix.

It should be emphasized that the national number is less important than the state-by-state numbers, because each state has a different risk pool that needs to have the proper mix of enrollees to remain viable.

On that front, West Virginia and Oregon had just 18 percent enrollment among that key demographic, whereas Utah was at 31 percent and the District of Colombia (which got a boost from an influx of congressional staffers) was at 45 percent.