Enrollment in Obamacare's new insurance exchanges rose to 4.2 million, but the percentage of young consumers signing up remained below targets despite the administration's efforts.

The Department of Health and Human Services announced the new figures Tuesday and pressed Americans to sign up during the last few weeks before open enrollment ends.

“Over 4.2 million Americans have signed up for affordable plans through the Marketplace,” said HHS Secretary Kathleen Sebelius in a statement. “Now, during this final month of open enrollment our message to the American people is this: You still have time to get covered, but you'll want to sign up today - the deadline is March 31st.”

The 4.2 million is a jump from the 4 million reported in late February. HHS said the exchanges saw a total of 943,000 sign-ups in the February period, but that was down from the 1.1 million who enrolled in January.

HHS said 1.6 million of the enrollees signed up through state-based marketplaces, with 2.6 million in federal exchanges.

The overall figure, though, is still well behind the administration’s target of 7 million enrollees on March 31. On that date, the individual mandate will kick in, subjecting those without health insurance to penalties.

Critics, though, say that the administration’s numbers don’t tell the full story and want more data on what percentage who have actually paid their first month’s premiums and how many were previously uninsured.

The figures also show a continued uphill struggle for the administration to sign up the young health consumers needed to offset older, sicker patients and keep the health law afloat.

The administration initially projected that 40 percent of sign-ups would be between the ages of 18 and 34, but the latest figures are well behind that target.

Twenty-seven percent of those who signed up in February on federal marketplaces were in that demographic, matching January’s percentage and ahead of the 24 percent mark from October through December.

Overall, 25 percent are between the ages of 18 and 34, the same level reported by the administration in mid-January.

The administration, though, is continuing their drive to reach more young people through new avenues. President Obama sat for a mock interview on the online spoof talk show “Between Two Ferns” with comedian Zach Galifianakis.

Critics said the video, first broadcast Tuesday, was not appropriate for a sitting president. It showed Obama making a serious attempt to plug his health care law in between trading insults and responding to the host's humorously misinformed questions.

But the White House defended the effort, saying that they were trying to “reach Americans where they live” and said the website that hosted the video was the number one referral site for traffic to healthcare.gov.

The administration is also making a push to get mothers to sign up their families to help boost enrollment in the final stretch.

The enrollment period has been plagued with numerous problems stemming from the rocky rollout of the healthcare.gov website in October, leading Republicans to charge that Obama’s signature domestic achievement was never ready for prime time.

The Obama administration has been forced to delay a number of key provisions in efforts to boost enrollment and assist insurers after Obama’s own broken promise that consumers could keep their current plans.

Reports suggested that hundreds of thousands could lose coverage because of new Obamacare regulations. Last week, the administration said that insurers could continue to offer plans that should have been cancelled for another two years.

Republicans suggested that it was a political move to lessen the blow for Democrats ahead of November’s crucial midterm elections, where Obamacare will be a key issue.

The White House has sidestepped questions about whether they will hit their unlikely 7 million target, saying only that they expect a surge in enrollments similar to Massachusetts, which also implemented health reforms.

“Based on enrollment patterns in other health care programs, it is expected that more people will sign up as we get closer to the March 31st,” said HHS in a statement.