WASHINGTON (NYTIMES, REUTERS) - President Donald Trump on Tuesday (April 28) declared meat processing plants "critical infrastructure", in an effort to ensure that facilities around the country remained open as the government tried to prevent looming shortages of pork, chicken and other products as a result of the coronavirus.

The action comes as meat plants around the country have turned into coronavirus hot spots, sickening thousands of workers, and after the head of Tyson Foods, one of the country's largest processors, warned that millions of pounds of meat would simply disappear from the supply chain.

In an executive order issued late on Tuesday, Mr Trump said recent closures of meat processing facilities "threaten the continued functioning of the national meat and poultry supply chain, undermining critical infrastructure during the national emergency".

The president said his administration would "take all appropriate action" to ensure that meat and poultry processors "continue operations" consistent with federal health and workplace safety guidance.

While Mr Trump said the step would ensure an ample supply of "protein for Americans", the announcement provoked swift backlash from unions and labour advocates, who said the administration needed to do more to protect workers who often stand shoulder to shoulder in refrigerated assembly lines. At least 20 workers have already died of the coronavirus, the United Food and Commercial Workers International Union said.

On Sunday, the Centres for Disease Control and Prevention and the Occupational Safety and Health Administration issued guidelines calling for physical distancing and other measures to keep workers safe. But the guidelines are voluntary, and food safety and labour advocates said they feared that meat companies would not follow them.

"Using executive power to force people back on the job without proper protections is wrong and dangerous," Mr Richard Trumka, the president of the AFL-CIO, wrote on Twitter, saying he echoed calls by the food workers union to "to put worker safety first".

Processing plants around the country have shut down amid outbreaks, putting a strain on the nation's slaughtering capacity and prompting food companies to warn of coming shortages at supermarkets. Farmers have begun killing pigs and chickens they can no longer sell to companies for processing.

As of last Thursday, 13 meatpacking and food processing plants had closed at some point in the past two months, resulting in a 25 per cent reduction in the nation's pork slaughter capacity and a 10 per cent reduction in beef slaughter capacity, according to the food workers' union.

In addition to the action, which was taken under the Defence Production Act, a Korean War-era law, the Labour Department and OSHA issued guidance that would provide additional liability protections for companies seeking to operate amid the risk of outbreaks.

In its statement, the agencies said the US government would weigh in on the side of companies who were facing litigation for reported workplace exposures to the coronavirus, as long as the companies were following the standards that the CDC and OSHA had issued for meat processing facilities.

The world's biggest meat companies, including Smithfield Foods, Cargill, JBS USA and Tyson Foods, have halted operations at about 20 slaughterhouses and processing plants in North America as workers fall ill, stoking global fears of a meat shortage.

Mr John H. Tyson, chairman of Tyson Foods, said on Sunday that the food supply chain was "breaking", and warned of the potential for meat shortages.

"We're working with Tyson ... We're going to sign an executive order today, I believe, and that will solve any liability problems," Mr Trump told reporters in the Oval Office. "And we always work with the farmers. There's plenty of supply."

Unions were not impressed. Some farmers said it was too late because pigs had been euthanised already instead of the pork going to market.

"While we share the concern over the food supply, today's executive order to force meatpacking plants to stay open must put the safety of our country's meatpacking workers first," said the United Food and Commercial Workers International Union in a statement.

UFCW, the largest US meatpacking union, demanded that the administration compel meat companies to provide "the highest level of protective equipment" to slaughterhouse workers and ensure daily coronavirus testing.

The senior administration official, speaking on condition of anonymity, said if action was not taken, the vast majority of processing plants could have shut down for a period of time, reducing capacity by as much as 80 per cent.

"This is part of our critical infrastructure," he said.

The order was little consolation for farmers such as Mr Henry Moore of Clinton, North Carolina, who in recent weeks aborted thousands of unborn piglets and euthanised newly born pigs because of closures of packing plants.

"At this point honestly it's a little too late," he said."There's millions and millions and millions of pounds of pork that will never make it to the market."

Administration officials and some Republicans on Capitol Hill have said that businesses that are reopening need liability protection from lawsuits employees might file if they become sick.

They cast it is a necessary prerequisite for business to have the confidence they need to reopen.

Senate Democratic Leader Chuck Schumer, speaking to reporters on a teleconference on Tuesday that mainly centred on immigrants working in the healthcare sector, was asked about Senate Majority Leader Mitch McConnell pushing for business liability protections as they reopen their operations.

"Is he saying if an owner tells a worker he needs to work next to a sick person without a mask and wouldn't be liable? That makes no sense," Mr Schumer said.