Updated 8:48 p.m. ET, 2/25/2014
(CNN) - Some 700,000 people have enrolled in Obamacare so far in February, raising total enrollment to roughly 4 million with a little more than a month to go before the sign-up deadline expires to get insurance this year.
The new figures for state and federal exchanges released by the Centers for Medicare and Medicaid Services on Tuesday illustrate participation in the sweeping initiative continues to grow steadily, a point raised by President Barack Obama at a White House event later in the day.
But the current pace indicates his administration will need a record month in March to reach a 6-million enrollment target, one that falls short of the original goal.
Obama's forecasts an all-out effort by his staff in coming weeks.
"We've only got a few weeks left," he told an Organizing for Action dinner in Washington Tuesday night, repeating the new total figure for emphasis.
"March 31, that's the last call. If folks aren't signed up by March 31, they can't sign up again until the next open-enrollment period with the 2015 rates," he said. "So if they want health insurance now, they need to sign up now, and we're going to make a big push these last few weeks."
The Obama administration initially hoped to sign up 7 million people by the end of March. But the non-partisian Congressional Budget Office estimate now stands at 6 million, and Vice President Joe Biden suggested earlier this month that it could trend lower.
"We may not get to seven, we may get to five or six, and that's a hell of a start," Biden said in Minneapolis.
The new numbers for February and overall also come as the administration appears to be scaling back expectations for enrollment of young adults.
For months, administration officials embraced CBO estimates anticipating that 18- to 34-year-olds would comprise roughly 40% of the total. The current number is about 27%.
The overall metric is critical for making the program work economically. The larger the pool of healthy, younger people paying premiums, the lower the cost of providing coverage for older, sicker participants.
White House spokesman Jay Carney said the 40% figure applied to the number of "uninsured who are young people."
"That's a little different from what you would need for the exchanges to have the demographic mix that's necessary for them to function effectively," he said.
Administration officials argued in January that Obamacare does not need to reach enrollment of 2.7 million young adults by the end of March to achieve a "sustainable market."
Asked about Carney's comments, a White House official cited a different metric from Massachusetts as a potential milestone.
"If you look at (Massachusetts), they never got above 34 percent in any given month as to the share of enrollees who were young adults and that was considered a successful risk pool," the official said.
A spokesman for House Speaker John Boehner, a chief critic of Obamacare, accused the White House of trying to move the goal posts.
"Obamacare enrollment goals are melting away as quickly as the law's deadlines. Youth enrollment has been a bust so far, and trying to whitewash stated benchmarks won't change that," Brendan Buck said.
White House officials note younger enrollment has accelerated in recent weeks, arguing that will improve the program's viability over time. The administration has tried to lower expectations for this key metric for several weeks.
Administration officials and advocacy groups have increased their enrollment drives, particularly looking to attract young adults and minorities.
Obama praised enrollment so far following the rocky rollout of the program in October when the federal government's HealthCare.gov website experienced a number of technical problems that held down enrollment.
"Four million people have already signed up because of you," Obama said at Tuesday night's event.
To explain why more people have yet to take advantage of newfound insurance access provided by the Affordable Care Act, Obama pointed to a well-funded opposition "that has spent hundreds of millions of dollars, if not billions of dollars spreading misinformation" about Obamacare.
Centers for Medicare and Medicaid Services Administrator Marilyn Tavenner said the latest numbers demonstrated "strong demand" for health insurance nationwide.
The administration will release a full enrollment report in mid-March, updating its February report.