With just four days left until the end of the open enrollment period, more than 6 million consumers have signed up for the health law's insurance exchanges, President Obama announced Thursday.

“This afternoon, while traveling in Italy, President Obama convened a conference call with health care navigators and volunteers helping with enrollment efforts and announced that more than 6 million Americans have signed up for private health insurance plans through the federal and state Marketplaces since October 1,” said the White House in a statement.

On the call, Obama spoke with thousands of volunteers and health officials working to enroll Americans in the exchanges before the March 31 deadline. After that date those without insurance will need to pay a penalty.

“During the call, the President thanked the group for all their hard work to date and discussed the importance of building on this progress over the last four days of open enrollment,” said the White House.

The administration touted “surging” interest in the exchanges and said healthcare.gov had over 1.5 million visits on Wednesday, and that there were over 430,000 calls to call centers.

“The President encouraged the navigators and volunteers to redouble their efforts over the next four days and leave no stone unturned in trying to bring affordable health coverage to as many Americans as possible,” the statement added.

The new figure shows a 1 million increase since the administration reported 5 million sign-ups 10 days ago, on March 17.

Enrollment efforts got off to a rocky start after the launch of healthcare.gov was plagued with numerous technical issues. The administration had initially targeted 7 million consumers by the end of March, but is still unlikely to reach that goal.

Figures also show the administration short on the number of young, healthy consumers needed to keep costs low and balance out the older, sicker consumers expected to flock to exchanges. Only a quarter of enrollees are young, short of the 40 percent mark the administration originally targeted.

The administration has also faced criticism after announcing that any individuals who tried to sign up before the deadline but were unable to complete their enrollment would be given time to finish the process.

Critics say that the administration is relying on an honor system and has no way of verifying that late applicants had tried to enroll before the deadline.

“We are not going to shut the door on people who were in line and could not get coverage through no fault of their own,” Centers for Medicare and Medicaid Services spokeswoman Julie Bataille told reporters on Wednesday.

Others also question how many enrollees have actually paid their first month's premium.