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President Donald Trump said Monday that he is suspending immigration to the United States in response to the coronavirus pandemic and the "need to protect jobs."

In a tweet Monday night, the president attributed the suspension to an "attack from the Invisible Enemy" and the "need to protect the jobs of our GREAT American Citizens."

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He added that he would sign an executive order suspending immigration.

Trump previously restricted travel from China and Europe to stop the spread of the coronavirus.

It's not clear from the president's tweet whether the order would bar non-U.S. citizens from traveling to the country for purposes such as business or to visit family.

White House officials offered few details Monday night.

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The move "had been under consideration for a while," a senior administration official told NBC News. The official said that although Trump believes the U.S. is winning the fight against the coronavirus, he also thinks it is important to make every effort to get ahead and protect the borders to prevent further spread.

The official said details about how the plan would be implemented and how many countries would be affected "will be forthcoming."

The executive order could be signed as early as this week, according to the administration official, who did not offer any details about whether it had been drafted or where the process stands.

Immigration has long been an issue that has energized the president's core supporters, and Monday night's tweet will undoubtedly be no different.

Immigration to the U.S. is already functionally shut down. The Trump administration had closed the U.S.-Canada border and started deporting asylum-seekers and other migrants on the southern border without due process. International air travel has largely been suspended.

Immigration advocates and activists criticized Trump's announcement, calling the move radical and unprecedented.

"The implication is that immigrants are a threat to the American economy, but we know the exact opposite to be true," said Krish O'Mara Vignarajah, president and CEO of Lutheran Immigration and Refugee Service. "While immigrants across America are on the front lines risking their lives to save ours, it is simply unconscionable to scapegoat immigrants for this pandemic."

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Sen. Kamala Harris, D-Calif., said the president was taking advantage of the situation to push his hard-line immigration policies.

"Trump failed to take this crisis seriously from day 1. His abandonment of his role as president has cost lives. And now, he's shamelessly politicizing this pandemic to double down on his anti-immigrant agenda," Harris tweeted.

The president said last month that he was discussing closing the country's borders with Mexico and Canada because of the virus. A senior official told NBC News then that the administration was exploring new restrictions amid fears that large numbers of Central Americans would try to illegally access the U.S. health care system.

According to data collected by Johns Hopkins University, Honduras has recorded 477 confirmed cases and 46 deaths, topping the so-called "northern triangle" countries — El Salvador, Honduras and Guatemala.

Reuters reported Monday that Peru has been the hardest-hit Latin American country, with more than 400 deaths and nearly 16,000 cases.

CORRECTION (April 21, 2020, 7:40 p.m. ET): An earlier version of this article mischaracterized President Donald Trump's previous orders on travel from China and Europe. The China order barred entry to the U.S. of most foreign nationals who had recently been in China; it did not ban all travel from China. The Europe order restricted entry to the U.S. of foreign nationals who had visited 26 countries in Europe that allow unrestricted movement; it did not ban all travel from Europe.