A key U.S. bishop expressed “strong opposition” on Wednesday to a new Republican-backed effort to slash legal immigration levels, cutting roughly in half the current number of more than a million foreigners every year receiving “green cards” allowing them permanent residency.

Called the RAISE Act (which stands for the “Reforming American Immigration for Strong Employment Act”), the measure introduced by two Senate Republicans was unveiled by President Donald Trump, who called it “a historic and very vital proposal.”

Within hours, Bishop Joe S. Vásquez of Austin, Texas, and Chair of the U.S. Conference of Catholic Bishops’ Committee on Migration, came out swinging against the proposal.

“Had this discriminatory legislation been in place generations ago, many of the very people who built and defended this nation would have been excluded,” Vásquez said, in a statement released late Wednesday by the bishops’ conference.

“The United States supports families, and should not throw up obstacles to their unity,” Vásquez said. “Unfortunately, the RAISE Act would have our nation turn its back on this long and storied tradition of welcoming families setting out to build a better life.”

Shortly after Trump’s endorsement, the Department of Homeland Security also came out in support of the RAISE Act, saying it “embodies the President’s vision for a merit-based immigration system that would better serve our national interest.”

The legislation would mark a major shift in U.S. immigration laws, which over the past half century have permitted a growing number of immigrants to come to the country to work or to join relatives already living here legally. Politically, it’s perceived to have dim prospects of passage in the Senate, where Republicans hold only a narrow majority.

However, political analysts in Washington say the logic for introducing the bill now may have less to do with its immediate prospects in the Senate, and more to do with shifting attention away from Trump’s recent setback on attempting to repeal the Obama-era Affordable Care Act and toward issues that resonate deeply with Trump’s political base.

The new proposal calls for steep cuts to family-based immigration programs that allow siblings and grown children of U.S. citizens and legal residents to apply for green cards. A point system based on factors such as English ability, education levels and job skills would be created to rank applicants for the 140,000 employment-based green cards distributed annually.

Trump praised that aspect of the proposal in particular, saying in a statement on Wednesday, “For decades, low-skilled and unskilled immigration into the United States has surged, depressing wages and harming America’s most vulnerable citizens.”

The proposal would also, according to Trump, prohibit recently-arrived legal immigrants ― green card holders, in other words ― from receiving welfare, although they would continue to pay into both the state and federal tax systems.

Currently, a majority of immigrants can’t get food stamps, Medicaid or Social Security from the government until they’ve resided in the country for at least five years.

Writing for New York, Ed Kilgore suggested there’s a thinly-veiled racism underlying the measure: “It’s about stopping demographic change, on behalf of people who see the mythological America of their youth slipping away,” he said.

For his part, Vásquez also objected to an element of the legislation that would impose new limits on admitting refugees.

“The RAISE Act would permanently cap the number of refugees allowed safe passage, thereby denying our country the necessary flexibility to respond to humanitarian crisis,” he said.

“I urge the Senate to reject this measure, and implore Congress and the President to work together in a bipartisan fashion to enact into law comprehensive immigration reform,” Vásquez  said.

“I believe that such reform must recognize the many contributions that immigrants of all backgrounds have made to our nation, and must protect the lives and dignity of all, including the most vulnerable,” he said.