The order is also expected to carve out additional exemptions for so-called essential employees, including health care workers, and immigrants who come into the United States through immediate family members, according to a person familiar with the situation.

Trump, who will sign the executive order as soon as Wednesday, said the measure will be reassessed in two months.

"It would be wrong and unjust for Americans laid off by the virus to be replaced with new immigrants, labor flown in from abroad," Trump said at the daily White House briefing, nodding to the 22 million Americans who have filed for unemployment in recent weeks. "We must first take care of the American worker, take care of the American worker."

Still, the president was short on details and indicated the order is still not final.

“It’s being written now,” Trump said. “We’ll most likely sign it tomorrow." He also hinted that he could sign a second order in the future, imposing further immigration restrictions, but provided no specifics.

The move angered conservatives who were hoping the president would go further. The Trump administration has already paused most routine visa processing and refugee cases during the coronavirus pandemic, meaning the president's executive order may be redundant for many already-stalled cases. Moreover, a majority of immigrants seeking green cards are already living in the U.S.

“Briefly delaying green cards for people, most of whom are already in the U.S. and working, and ignoring work visas doesn't help U.S. workers and doesn't ease pressure on hospitals, “ said Mark Krikorian, executive director of the Center for Immigration Studies. “Can't know for sure until there's actually something official to read, but this looks more like a political gesture than a serious policy move.”

Soon after Trump finished speaking, Fox News host Tucker Carlson, who occasionally advises the president, blasted the effort, saying Trump “failed” to protect American jobs.

Conservatives have been pushing Trump for weeks to stop allowing temporary foreign workers into the United States during the pandemic. But so far, the president has sided with business leaders who argue immigrant workers are still needed, even with so many Americans out of work, to preserve the food supply and keep other industries staffed.

Last week, Trump asked aides last week to look into the possibility of pausing all immigration during the coronavirus outbreak, seeking a bold step he could announce amid ongoing criticism of his response to the pandemic.

Trump’s request to look into the potential executive order, described by three people familiar with the situation, ultimately led to the tweet late Monday night in which Trump declared he would be temporarily suspending all immigration. The result will not be nearly as dramatic as the tweet sounded.

Yet if the executive order remains in place through the fall, Trump could once make immigration a centerpiece of his campaign, the way he did in 2016 when promised to build a wall on the southern border with Mexico and deport millions of migrants who arrived in the country illegally. During the pandemic, Trump has also restricted foreign visitors from China, Europe, Canada and Mexico, and frequently touts those decisions.

An outside Trump adviser said Trump felt the latest change was needed to rebuild the economy. “This is middle-class driven,” the person said. “That’s what needs to be rebuilt fast.”

As the outbreak has spread, the Trump administration has quietly continued to allow foreign workers to enter the country, even easing requirements for immigrants to get certain jobs — allowing electronic signatures and waiving the physical inspection of documents.

On Friday, the administration temporarily removed some limitations on agricultural workers, including allowing them to stay in the United States beyond the three years maximum limit.

In early April, under pressure from immigration activists, the administration did backtrack on a plan to pause the approval of 35,000 more seasonal worker visas, pending further review.

“To continue most immigration at this time would show a callous disregard for those Americans who are enduring deep economic suffering,” said Roy Beck, president of NumbersUSA, which supports immigration restrictions.

Trump and his aides also said the plan would promote safety during the pandemic, but he didn't explain how. It's also unclear how the move would safeguard Americans against the virus when some immigrants will still be able to come into the country.

Economically, the president might have struggled to sell a complete ban on immigrants.

In the U.S., immigrants make up 17 percent of healthcare workers, 24 percent of direct-care workers, including the nurses and assistants, and 28 percent of high-skilled professionals in the field, including physicians and surgeons, according to Envoy Global, an immigration services provider.

Trump's announcement had his critics decrying the move as a transparent attempt to rile up the president's base in an election year, while distracting from the ongoing criticism of his coronavirus response.