WASHINGTON (REUTERS) - A plan by President Donald Trump to temporarily block some foreigners from permanent residence in the United States is still undergoing legal review, which could delay its signing, according to White House aides on Wednesday (April 22).

Trump says the order, which could affect thousands of people hoping to settle in the United States, will protect American workers during the novel coronavirus pandemic.

White House adviser Kellyanne Conway told reporters the review could potentially delay a planned signing on Wednesday.

"It has to be cleared legally," Conway told reporters.

"I know he's itching to sign it, but it's a matter of when it's ready," she said.

Trump, a Republican, won the White House in 2016 in part on a promise to crack down on immigration and has made the issue central to his presidency. But many of his major moves trying to curb immigration have been challenged in court and legal experts said this executive order could also face lawsuits.

Many key details of Trump's planned executive order are still not known, but one US Department of Homeland Security official who requested anonymity said it would only apply to people applying for permanent residence from outside the United States, not those already in the country seeking to adjust their status.

Trump said the order initially would last for 60 days and could be renewed for the same period or longer, and that a second immigration-focused order was under consideration.

Critics saw his announcement as a move to take advantage of the coronavirus crisis to implement a long-sought policy goal of barring more immigrants ahead of this year's presidential election.

A person familiar with the internal debate at the White House said Trump and his advisers had discussed the executive order over the weekend and that the move was directed at his electoral base.

"He's wanted this all along," the person said. "But now under this pandemic he can absolutely do it."

Trump wrote on Twitter on Wednesday morning that he planned to sign the order later in the day. White House Press Secretary Kayleigh McEnany said Trump was still expected to sign the order sometime on Wednesday but that it was being finalised.

McEnany pushed back on reports that a rough draft was put together after the president tweeted on Monday night that he would be temporarily suspending immigration into the United States.

"That absolutely is not the case," she said. "In fact, I read the draft before the tweet even went out. So this has been in the works for quite some time."

A senior administration official said that if the signing of the order was delayed beyond Wednesday, it would be to resolve relatively narrow issues, such as whether the ban should apply to special visas for Iraqi translators and interpreters who assisted the US government in that country.

CONFUSION

Immigration attorneys representing businesses expressed opposition to Trump's plan on Tuesday, arguing it would only further depress the economy.

Michael Clemens, a senior fellow at the Washington-based Centre for Global Development, said that a range of industries would be hurt including ones that are critical during a public health emergency such as food processing, warehousing, shipping, eldercare, childcare, communication and technology.

Many of those jobs are filled by immigrants and the family members they reunite with from abroad, he said.

"Immigrants are the backbone of these industries," Clemens said.

Most US immigration services are largely already on pause due to the crisis, but immigration lawyers - including those representing financial and tech firms - around the country fielded calls on Wednesday from applicants and employers worried about the possible order.

The Washington-based Migration Policy Institute estimated that Trump's green card effort could prevent between 114,000 and 660,000 people securing permanent residence - if left in place for a year.

Democrats and immigrant advocates have criticized the new policy as an attempt to distract from Trump's response to the coronavirus pandemic as he seeks re-election in November. More than 45,000 people in the United States have died because of the virus, according to an analysis of official data by Reuters.

That is the highest death toll of any country.

Some immigration hawks criticized the order, as described by Trump on Tuesday, for not going far enough.

"It doesn't apply to guestworkers, which are perhaps the most immediately threat to US workers," said Mark Krikorian, executive director of the Centre for Immigration Studies, which backs lower levels of legal immigration.

While Trump has cast the measure as a response to the outbreak, it also may accomplish a long-sought goal of limiting legal immigration, particularly immigration based on family ties. More than half of the roughly one million green cards granted each year go to family members of US citizens or permanent residents.