President Trump on Wednesday signed a proclamation to temporarily suspend certain visas for foreigners seeking to move permanently to the U.S., decreeing that the admission of new immigrants would hurt American workers already struggling in an economy ravaged by the coronavirus pandemic.

The 60-day restriction, which will take effect Thursday night, applies to people overseas seeking to become U.S. permanent residents through petitions filed by their family members or employers in the U.S. The order also pauses the diversity visa lottery, a frequent target of Mr. Trump's ire. Since it restricts family-based immigration, the main way people move permanently to the U.S., the proclamation is expected to block the entry of tens of thousands of people, according to experts.

In his decree, Mr. Trump said the restrictions were needed to prevent large numbers of new immigrants from competing with U.S. workers in the labor market. He specifically referenced the impact of the economic downturn on African Americans and other minorities, suggesting more immigration would hurt those communities.

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"These are the workers who, at the margin between employment and unemployment, are likely to bear the burden of excess labor supply disproportionately," the president wrote in his proclamation.

The non-partisan Migration Policy Institute estimates that 52,000 would-be immigrants will lose their chance to obtain U.S. green cards over two months, the order's initial time span. The president's proclamation said the restrictions could be extended beyond 60 days "as necessary," and charged the U.S. Department of Homeland Security to review them after 50 days of implementation.

By significantly restricting family-based immigration, which Mr. Trump and restrictionists deride as "chain migration," the proclamation accomplishes one of the administration's long-sought legislative objectives, at least temporarily.

"These categories significantly parallel categories that we've seen the president try to restrict in the past," Sarah Pierce, a policy analyst at the Migration Policy Institute, told CBS News. "It is far more likely the president is just trying to accomplish unilaterally what he couldn't accomplish without the Congress."

Pierce said the president is likely to extend the proclamation, calling the 60-day period somewhat insincere: "Clearly the economic downturn is going to last longer than 60 days. I fully expect that he expects these restrictions to be more permanent."

The order contains some exceptions, including for spouses and minor children of U.S. citizens, some health care workers, certain investors and military family members. It also excludes immigrants who obtain permanent residency through the nation's asylum and refugee programs.

Despite initial reports that the president's order could target guest worker programs, the directive unveiled Wednesday does not restrict any non-immigrant visas, which can allow technology workers, students, agricultural workers and other foreigners to work and live in the U.S. for a limited period of time. Some anti-immigration activists usually aligned with the administration's agenda said the order did not go far enough, since it did not ban temporary workers as well.

The U.S. Departments of State and Homeland Security did not respond to requests to elaborate on how officials will enforce the presidential directive.

The immediate practical impact of the proclamation may be limited initially as the Trump administration had already tightened the country's borders in response to the deadly pandemic, which has killed more than 47,000 people in the U.S.

Visa processing for both would-immigrants and prospective workers abroad has been extremely limited since March 20, when the State Department, which oversees consular officers, canceled most appointments at U.S. consulates and embassies. Admissions of new refugees have been paused since March 19, with the exception of certain "emergency" cases, a State Department spokesperson told CBS News on Tuesday.

Non-essential travel through ports of entry along the land borders with Mexico and Canada has been banned since March. The U.S. Department of Homeland Security renewed those restrictions Monday. In January, the president restricted travel from China and extended those restrictions to most of western Europe in early March.

By invoking a World War II-era public health law, officials at the U.S.-Mexico border have also been expelling thousands of unauthorized migrants and asylum-seekers, including unaccompanied migrant children, who are afforded extra legal safeguards under U.S. anti-trafficking and immigration laws.

Through these restrictions, which were also renewed Monday, the U.S. — for the first time since the creation of the nation's asylum and refugee regime in 1980 — has stopped offering protection to those who claim fear of persecution in their home countries.

U.S. Immigration and Citizenship Services has suspended in-person appointments at all its field offices, preventing green card holders from naturalizing and becoming U.S. citizens.

Mr. Trump has previously invoked the broad U.S. immigration law provision he cited in Wednesday's order. It allows him to ban foreigners by proclamation if he determines their entry could be "detrimental to the interests" of the U.S.

That was the legal justification behind his administration's travel ban upheld by the Supreme Court in 2018, as well as a directive last year banning the entry of would-be immigrants whom officials determine won't be able to afford health insurance or medical treatment in the U.S.

Omar Jadwat, director of the American Civil Liberties Union's Immigrants' Rights Project, said Wednesday's order displayed Mr. Trump's inept leadership, arguing that the president should be focusing on other ways to protect people in the U.S. during the pandemic, like releasing immigrant detainees. Still, he said the proclamation would have real, adverse consequences.

"While the order is limited in scope, President Trump's transparent attempt to distract from his own failures with this unwarranted suspension will cause real pain for families and employers across the country," Jadwat said in a statement.