President Trump said Wednesday that he strongly disagreed with Georgia Gov. Brian Kemp’s decision to authorize the reopening of small businesses, saying it was too soon to do so and that opening the businesses violated federal guidelines.

Trump said he spoke Wednesday to Kemp (R), who has authorized the reopening of businesses including hair salons and tattoo parlors. Trump said he told Kemp that “I disagree, strongly, with his decision to open up facilities which are in violation of the Phase I guidelines. At the same time,” he said, Kemp “must do what he thinks is right.”

In several tweets, Kemp defended his decision. “I appreciate his bold leadership and insight during these difficult times and the framework provided by the White House to safely move states forward,” Kemp said of Trump.

“Our next measured step is driven by data and guided by state public health officials. We will continue with this approach to protect the lives — and livelihoods — of all Georgians. Just like the thousands of businesses currently operating throughout Georgia, I am confident that business owners who decide to reopen will adhere to Minimum Basic Operations, which prioritize the health and well-being of employees and customers,” Kemp said.

In a news conference Monday, Kemp said that Georgians would be allowed Friday to visit gyms; hair, nail and massage salons; and tattoo parlors and that restaurants and movies could open next week. He said social distancing and hygiene rules should still be enforced, but he believed the crisis in Georgia, where there have been nearly 20,000 confirmed cases of the virus, had leveled off enough to ease the restrictions. A number of mayors in the state have strongly disagreed, and some have called on citizens to ignore him.

The federal guidelines, released last week, emphasize that they are “implementable . . . at governors’ discretion,” and Trump has stressed repeatedly that they are voluntary. They outline three phases for reopening, with only limited easing during the first phase and maintenance of social distancing that would prevent the close contact of personal grooming establishments. “We’re going to have Phase II very soon,” h said.

While he emphasized that Kemp should make his own decision, he said he believed “it’s too soon. They can wait a bit longer. . . . Safety has to predominate.”

Trump, speaking at Wednesday’s White House briefing, said that he was talking to a number of governors about their plans to reopen. “It’s a beautiful thing to see,” he said of the easing of restrictions, but “I encourage governors to follow a careful approach.”

Anthony S. Fauci, the infectious disease expert and White House virus adviser, said he, too, would advise against the measures Kemp has taken. Recovery is “not going to be ‘turn the lights on in America, we’re finished,’ ” Fauci said. The guidelines “are measured,” he said, and there are “certain things before you can even think of going to Phase I. . . . If we don’t do it in a measured way, there is a likelihood that we will have a rebound.”

Trump said Wednesday that the nation was starting to “open for business again,” and Treasury Secretary Steven Mnuchin predicted that “most of the economy” would be operational by late summer.

Trump early in the day tweeted his enthusiasm for easing restrictions, saying: “States are safely coming back. Our Country is starting to OPEN FOR BUSINESS again. Special care is, and always will be, given to our beloved seniors (except me!) Their lives will be better than ever....WE LOVE YOU ALL.”

In an interview on Fox Business Network, Mnuchin said: “I hope we are going to get back to work fairly quickly. . . . And we’re looking forward to, by the time we get later in the summer, having most of the economy, if not all of the economy, open.”

But many states have held firm. California Gov. Gavin Newsom laid out plans to expand testing but said the shutdown must continue. “I deeply recognize, deeply understand the desire for people to hear directly from the administration, from the state and its leadership, about the answer to when, when can we go back to some semblance of normalcy,” Newsom (D) said in a news briefing. He said that testing had been delayed by a shortage of swabs but that new orders were expected to arrive this week. He also laid out a plan to train 10,000 people to track virus patients, adding that the results of those actions would dictate when the shutdown can ease.

The optimistic assessments from Trump and Mnuchin came as new information indicated that the first U.S. death from the virus occurred in early February, weeks earlier than previously thought. Health officials in California said two people died at home in Santa Clara County on Feb. 6 and Feb. 17 but that testing of their remains for the infection had been delayed.

The revelations shifted the timeline in this country of the virus’s arrival and spread, which has now caused more than 47,000 deaths. Meanwhile, doctors across the nation were discovering and sharing information on puzzling peculiarities of the disease, originally thought primarily to affect respiration. In many patients, it also causes mysterious blood-clotting complications in organs throughout the body, which may be the reason death has often appeared so suddenly, even in patients without severe symptoms.

News about the pandemic, the economic and social havoc it has wreaked, and the likelihood of an early recovery continued its roller-coaster trajectory.

Governments in Germany and Britain approved human testing of potential vaccines against covid-19, the disease caused by the coronavirus, and some trials were slated to begin as early as this week. A Boston hospital reported that it had figured out how to produce up to a million swabs daily for virus tests — supplying a commodity whose scarcity has slowed the rate of testing — with the help of 3-D printers.

New York Gov. Andrew M. Cuomo (D), who discussed the testing issue Tuesday with Trump in Washington, said Wednesday that he and the Democratic governors of New Jersey and Connecticut were launching an “ambitious” program to test, trace and isolate infected people. The spread has diminished in countries where testing and tracing the contacts of those infected, followed by isolation, have been far more extensive than the United States.

Former New York mayor and Democratic presidential candidate Mike Bloomberg has volunteered to contribute $10 million and to develop the “first-ever testing, tracing and isolation program” in the state, Cuomo said.

Cuomo, while not announcing any easing of the New York lockdown, has started to outline the early stages of a reopening.

Trump said that national parks, many of which have been closed, would reopen as long as Americans “continue to take reasonable precautions, and hopefully it will be just reasonable.” He gave no timeline for the openings.

White House trade adviser Peter Navarro said that Trump would “move swiftly” to expand use of the Defense Production Act to boost private production of medical supplies, including swabs, for the pandemic, as well as future crises.

Critics have accused Trump of being too slow to use his power to enforce the act, which allows the president to order private companies to produce critical items.

Food and Drug Administration Commissioner Stephen Hahn also said that testing capacity could increase nationwide as new at-home testing kits became available. The tests, which Hahn told “CBS This Morning” are as effective as those administered in a doctor’s office, will first be provided to health-care workers and front-line virus responders, he said, but are part of the overall effort to increase testing numbers.

Global stock markets rebounded after a two-day fall that was largely due to the drop in oil prices. In the United States, where the Dow Jones industrial average closed more than 450 points higher, the positive move was seen primarily as a response to the governors of states including Georgia, Florida, South Carolina, Texas and Ohio saying that they planned to reopen at least parts of their economies in the coming days.

A South Dakota racetrack said it would hold an auto race as scheduled Saturday, with limits on the number of ticket sales. Gov. Kristi L. Noem (R), who has not issued a stay-at-home order, nonetheless strongly recommended “to the people of South Dakota that they don’t go and that they stay home” for several more weeks.

A spike in the virus threat led to the closure of another pork production plant, Tyson Fresh Meats in Waterloo, Iowa. Tyson’s largest pork plant, representing about 4 percent of the nation’s processing capacity, employs 2,800 and processes 19,500 hogs a day.

The closure, following earlier shutdowns at plants run by Smithfield Foods, JBS USA and other companies, added to concerns about the nation’s meat supply.

As the pandemic continued to upend lives around the world, the World Bank said global remittances — the money that foreign workers send home — were expected to fall by 20 percent, or nearly $110 billion, this year as unemployment grows. Many families in low-income countries depend on the remittances from relatives in wealthier places such as the United States and the Persian Gulf.

In Washington, Secretary of State Mike Pompeo continued to attack the World Health Organization for failing to press China for information on the virus’s origin and a lack of transparency. China, he said at a State Department news conference, failed to adhere to international rules that obligate it to “communicate to WHO timely, accurate and sufficiently detailed public health information.”

Instead, he said, China “covered up how dangerous the disease is. It didn’t report sustained human-to-human transmission for a month until it was in every province inside of China. It censored those who tried to warn the world, it ordered a halt to testing of new samples, and it destroyed existing samples.”

The same international rules, he said, “also gave the director-general of the WHO encouragement and the ability to go public when a member country wasn’t following those rules, and that didn’t happen in this case, either.”

The WHO, Pompeo said, “clearly failed during this pandemic.”

Other governments, and some U.S. lawmakers, have said that the WHO could have acted more strongly but that it lacks the power to force member countries to do its bidding. Some have suggested that Trump has used the WHO to distract criticism of the administration’s performance.

In Geneva, WHO Director General Tedros Adhanom Ghebreyesus defended the agency’s work and warned that the pandemic would be “with us for a long time.”

“Most countries are still in the early stages of their epidemics,” he said, adding that there were “worrying upward trends” in Africa, Central and South America and Eastern Europe.

He warned that public unrest against social distancing measures now seen in the United States and other countries “will only fuel the outbreak.”

Mike Ryan, the organization’s chief emergency expert, said that he had seen in the past that genuine public concerns could be deliberately inflamed.

“There are many situations in which those reactions and community sentiments are gamed and directed in a way that is counterproductive,” Ryan said, comparing the demonstrations during the coronavirus outbreak with protests he had seen against anti-Ebola measures in Congo.

Adam Taylor, Toluse Olorunnipa, Lateshia Beachum, Miriam Berger, Cindy Boren, Rachel Siegel, Felicia Sonmez, Ariana Eunjung Cha, Allyson Chiu and Teo Armus contributed to this report.