The powerful Koch network is ramping up its last-minute lobbying to get permanent protections for young immigrants known as “dreamers” in a must-pass spending bill.

In a letter Tuesday to congressional leadership, top officials from three Koch-backed groups — Americans for Prosperity, Freedom Partners and the LIBRE Initiative — pressed Congress to include $25 billion in border security cash paired with a pathway to citizenship for young undocumented immigrants who came here as minors. That offer had been floated by congressional Democrats in recent days.

In short, “a historic moment is upon us, and we urge you to seize it,” the groups wrote to the four congressional leaders: House Speaker Paul D. Ryan (R-Wis.), House Minority Leader Nancy Pelosi (D-Calif.), Senate Majority Leader Mitch McConnell (R-Ky.) and Senate Minority Leader Charles E. Schumer (D-N.Y.).

“We believe this is a reasonable proposal — one that should be supported by the president and members of Congress in both parties,” the groups wrote in the letter, provided to The Washington Post in advance of its release. “It’s now time to cast aside partisan differences and support a solution that provides certainty for dreamers, who were brought as children to the United States and seek the opportunity to apply their skills and talents in this country.”

Officials who signed onto the letter included Brent Gardner from Americans for Prosperity, Daniel Garza from the LIBRE Initiative, and Nathan Nascimento from Freedom Partners Chamber of Commerce. The groups had released statements Monday pressuring the White House and Capitol Hill to take that proposal from Democrats, a noteworthy pitch from the influential network that typically pushes conservative causes.

President Trump has continued to push for a deal in the omnibus spending measure that would temporarily protect young immigrants without legal status in exchange for a funding for his long-prized border wall. Democrats have rebuffed that pitch, and its inclusion in the spending bill appeared highly unlikely as of Tuesday, although the final bill has not been released.