WASHINGTON (REUTERS) - The White House on Sunday (March 15) urged Americans against "hoarding" as thousands flocked to supermarkets to stock up on essentials, saying US supply chains were strong and federal and local leaders were working together to ensure food supplies are available.

US President Donald Trump held a phone call with more than two dozen grocery store and supply chain executives from across the country, White House spokesman Judd Deere said in a statement.

"The President reminded the participants that this is an all-of-America approach and each of their stores and the stores they support can help Americans feel calm and safe when shelves are stocked with the items they need," Deere said.

"Supply chains in the United States are strong, and it is unnecessary for the American public to hoard daily essentials," he said.

The call was held with 30 executives including senior leaders of some of the largest US retailers such as Whole Foods, Target, Costco and Walmart.

Americans have been emptying store shelves for days. But for many, the severity of the rapidly spreading coronavirus, which causes the sometimes fatal, highly contagious respiratory illness Covid-19, really started to sink in after Trump declared a national emergency on Friday, releasing US$50 billion in federal aid to help states fight the virus.

In the United States, the disease has infected more than 3,200 people and killed at least 62. More than 154,000 people have been infected worldwide, and some 5,800 have died since the virus was discovered in China in December.