Then-President Barack Obama speaks to the media during a Dec. 16, 2016, news conference at the White House. (Andrew Harnik/AP)

Former president Barack Obama posted a nearly 1,000-word critique of the Senate health-care bill Thursday on Facebook, warning, “This bill will do you harm.”

While Obama has repeatedly defended the Affordable Care Act, which represents perhaps his most significant domestic legislative achievement, Thursday’s statement was even more pointed than his previous comments. Calling the GOP leadership’s bill “a massive transfer of wealth from middle-class and poor families to the richest people in America,” he called on Americans to push back against congressional Republicans.

“Simply put, if there’s a chance you might get sick, get old, or start a family — this bill will do you harm,” the former president wrote. “And small tweaks over the course of the next couple weeks, under the guise of making these bills easier to stomach, cannot change the fundamental meanness at the core of this legislation.”

While the ACA was passed without Republican support in either the House or Senate, Obama emphasized that many ordinary Republicans had reasons to support the measure: “intensely personal ones” that included a sick relative or concerns about massive medical bills.

A health-care bill released June 22 by the Senate Republican leadership faces opposition from Democrats as well as four GOP senators, making the proposal's fate uncertain. (Alice Li,Jorge Ribas,Libby Casey,Bastien Inzaurralde/The Washington Post)

“So I still hope that there are enough Republicans in Congress who remember that public service is not about sport or notching a political win, that there’s a reason we all chose to serve in the first place, and that hopefully, it’s to make people’s lives better, not worse,” he wrote.

And Obama called on Americans to lobby their senators, in order to slow down the Republican bill’s consideration and pressure GOP lawmakers into negotiating with Democrats on the proposal. Constituents could influence the process, he wrote, “If you’re willing to call your members of Congress. If you are willing to visit their offices. If you are willing to speak out, let them and the country know, in very real terms, what this means for you and your family.”