Facebook CEO Mark Zuckerberg and COO Sheryl Sandberg are urging Congress to pass legislation protecting American immigrants known as Dreamers.

"The United States is not a cruel country. But what we're considering doing to Dreamers is cruel. They deserve the chance to earn citizenship and legal protection to keep them safe and keep their families together," Sandberg wrote in a Facebook post on Wednesday.

It's a precarious time for Dreamers.

Friday marks the deadline for a new government spending plan. And Democrats have been holding off on agreeing to a spending deal until there's a legislative fix for Dreamers, or undocumented immigrants who came to the United States as children.

They'll soon become vulnerable because President Trump said he would end the Deferred Action for Childhood Arrivals program, which shielded Dreamers for deportation and allowed them to enroll in college and legally secure jobs. At the time, the government gave Congress six months to come up with a pathway to help Dreamers stay in the United States.

Last week, a bipartisan group of lawmakers met at the White House to present an immigration plan that included protection for Dreamers, but Trump rejected it. Some Republicans have argued that a bill involving DACA should be paired with other immigration pushes to deter illegal immigration, such as increased boarder security.

If Congress doesn't pass a solution before the March deadline, an average of nearly 30,000 people a month for the two years following the termination of the program would lose their protection from deportation, according to a CNN analysis of Department of Homeland Security data.

"The average DACA recipient came to this country at age six and has lived here for 20 years. They've gone to American elementary and high schools," wrote Sandberg. "They work and live in every state. Some serve in our military. And now they face the very real possibility of being sent away from the country they call home."

Related: Tim Cook: I'm personally shocked there's even a debate on DACA

Sandberg posted shortly after Zuckerberg on Wednesday. He said this is an instance that will showcase whether our government actually works.

"Can Congress come together and find a path forward, or will we default to forcing almost one million people out of their jobs and country?" he wrote. "I'm optimistic this will get solved. There's been some good bipartisan momentum on legislation recently. From my conversations with leaders in Congress, I believe they want to fix this, but we need to keep the pressure on so they know we'll hold them accountable."

Zuckerberg, who called the administration's decision to end DACA "particularly cruel," is also the cofounder of FWD.us, an immigration advocacy organization.

It's just the latest reminder of Silicon Valley's tension with the Trump administration, whose immigration policies have stung an industry where immigrants have played integral roles in the founding, and continued successes, of big name companies.