Washington (CNN) Former President Barack Obama praised members of his administration for "continuing to fight for an America that's better" after nearly 150 African Americans signed an op-ed slamming President Donald Trump for his recent racist attacks targeting four progressive Democratic congresswomen of color.

"I've always been proud of what this team accomplished during my administration. But more than what we did, I'm proud of how they're continuing to fight for an America that's better," Obama, who has been notoriously restrained since leaving office when it comes to publicly speaking out about Trump's policies and behavior, wrote on his Twitter account on Saturday. Obama's former senior adviser Valerie Jarrett was also a signatory of the op-ed.

In the op-ed, published on Friday in the Washington Post, former members of Obama's administration signaled their support for the four Democratic congresswomen that Trump targeted and said the current president is "complicit in the poisoning of our democracy."

"We stand with congresswomen Ilhan Omar, Alexandria Ocasio-Cortez, Ayanna Pressley and Rashida Tlaib, as well as all those currently under attack by President Trump," the op-ed reads. "There is truly nothing more un-American than calling on fellow citizens to leave our country."

Earlier this month, Trump -- in racist language that was later condemned by a House resolution -- told the four progressive Democratic congresswomen of color to "go back and help fix the totally broken and crime infested places from which they came." Three of the four were born in the US, and the fourth is a naturalized US citizen. On Saturday, Trump unleashed a new assault against Democratic Rep. Elijah Cummings -- chairman of the House Oversight Committee and frequent critic of the President -- tweeting that his Baltimore district is a "disgusting, rat and rodent infested mess."

Read More