Former President Barack Obama and former first lady Michelle Obama on Monday urged Obamacare customers to sign up for coverage ahead of the open enrollment deadline Friday.

"Just got off a call to thank folks who are working hard to help more Americans across the country sign up for health coverage," the former president tweeted. "But it's up to all of us to help spread the word: Sign up through this Friday at ."

Michelle Obama, who hasn't tweeted about Obamacare since open enrollment began, wrote, "Getting covered means getting peace of mind for yourself and your family. So sign up today and tell everyone you know that Friday is the last day to sign up for coverage at HealthCare.gov."

The tweet is the second that the former president has sent since the start of open enrollment, which began Nov. 1. President Trump hasn't sent any tweets about open enrollment, and one was sent by Seema Verma, the administrator for the Centers for Medicare and Medicaid Services, the agency that oversees open enrollment.

Trump has said he does not support Obamacare and plans to work with Congress to overhaul it in 2018. The tax plan being advanced by Republicans would repeal the penalties for Obamacare's individual mandate, which require eligible Americans to buy health insurance or pay a fine.

The Trump administration also made several changes to this year's open enrollment. Under Obama, open enrollment lasted 90 days or even longer during the first several years as the website was plagued by technical difficulties. The Obama administration had planned to reduce open enrollment to 45 days by 2018, but the Trump administration moved it up a year.

Former health officials from the Obama administration have been running media campaigns to alert people to sign up for coverage and have taken to social media to write about the types of plans offered. The Trump administration cut funding for advertising and outreach, saying that navigators should be paid according to the number of people they are able to get to sign up for coverage.

In 2016, the data show, navigators received $62.5 million in federal grants to enroll 81,426 people, which represents 0.7 percent of total Obamacare enrollees.

Despite that, supporters of Obamacare have said the Trump administration is trying to "sabotage" the law and said that they fear fewer people will enroll in coverage because they won't know about it or won't receive enough help.

As of Dec. 2, 3.6 million people have enrolled in Obamacare plans.