Washington, D.C. — More than 100 members of Congress denounced an abrupt and publicly unannounced move by the Trump administration to shutter a program that has shielded hundreds of seriously ill immigrants and their families from deportation while they receive life-saving medical treatment in the U.S.

The contingent of Democratic lawmakers from both the House and Senate penned a letter on Friday to top officials at the Department of Homeland Security, urging them to reverse course and continue offering these immigrants — including children with life-threatening health conditions — a temporary reprieve from deportation through a U.S. Citizenship and Immigration Services (USCIS) program known as medical deferred action.

The decision to end the program "will needlessly endanger vulnerable children and families nationwide seeking medical deferments for individuals receiving life-saving treatment for serious illnesses," the lawmakers wrote.

16-year-old Jonathan Sanchez is in the U.S. getting treatment for cystic fibrosis. But this week, his family received a notice, giving them 33 days to leave the country or face deportation. CBS News

In their letter, 110 members of Congress asked leadership at the Department of Homeland Security to clarify the policy shift, explain the rationale behind it, say why the public and Congress were not notified and address concerns that the end of the program could result in people being deported to countries which lack adequate medical treatment options for their conditions.

Get Breaking News Delivered to Your Inbox

The letter was spearheaded by Representatives Ayanna Pressley and Mark DeSaulnier of Massachusetts; Zoe Lofgren, Judy Chu and Lou Correa of California; and Massachusetts Senators Ed Markey and Elizabeth Warren, who is also running for president.

Earlier this month, immigration attorneys and their clients who applied for medical deferred action or a renewal of it began receiving rejection letters in which USCIS said it was no longer considering requests for the program. The letters also said immigrants not authorized to remain in the country should leave within about month or face deportation.

Like the more commonly known Obama-era Deferred Action for Childhood Arrivals (DACA) initiative for undocumented immigrants who came to the U.S. as children, medical deferred action was part of small set of temporary relief options offered by USCIS. The immigrants granted this reprieve would not be prioritized for removal by the government, which would exercise prosecutorial discretion.

A USCIS official confirmed to CBS News that starting on August 7, the agency had ceased to process non-military deferred action requests as part of an effort to "focus agency resources on faithfully administrating" the nation's "lawful immigration system."

"Because USCIS is not an enforcement agency, it is not appropriate for the agency to adjudicate requests for suspended enforcement not clearly assigned to USCIS in law or policy," the official said.

The agency said it has received about 1,000 deferred action requests a year, but that the "majority" have been denied. Going forward, the official said USCIS will defer to Immigration and Customs Enforcement (ICE) so that agency — which is in charge of removing people from the country — can determine whether to grant non-military deferred action.

In a statement to CBS News, ICE said it has the discretion to determine which individuals will be prioritized for deportation. But an agency official said ICE does not accept "applications" for deferred action.

Democrats in their letter on Friday criticized the decision by USCIS to "abandon its longstanding responsibility" for deferred action petitions and to effectively outsource that relief option to ICE — which the lawmakers said many undocumented immigrants fear.

"Requiring that prospective applicants request this humanitarian relief by applying to an immigration enforcement agency that detains and deports hundreds of thousands of immigrants annually, will deter many vulnerable children and families from coming forward and seeking life-saving protection," the lawmakers wrote.

Angelica Fusco contributed to this report.