The World Health Organisation (WHO) has said rushing to ease coronavirus restrictions will likely lead to a resurgence of the illness.
The warning comes as governments across the world start rolling out plans to get their economies up and running again.
Dr Takeshi Kasai, the WHO regional director for the Western Pacific, said: “This is not the time to be lax. Instead, we need to ready ourselves for a new way of living for the foreseeable future.”
Despite concerns from health officials, some US states have announced aggressive reopening plans, while Boeing and at least one other American heavy-equipment manufacturer resumed production.
Elsewhere around the world, step-by-step reopenings are under way in Europe, where the crisis has begun to ebb in places such as Italy, Spain and Germany.
Australia said it will allow the resumption of non-urgent surgeries from next week as health authorities grow more confident that hospitals there will not be overwhelmed by Covid-19 patients.
Asian shares followed Wall Street lower on Tuesday after US oil futures plunged below zero because of a worldwide glut as factories, with cars and aeroplanes not being used.
The cost to have a barrel of US crude delivered in May plummeted to negative 37.63 dollars as traders run out of places to store it. It was at roughly 60 dollars at the start of the year.
Businesses which start operating again in the US are likely to engender goodwill with President Donald Trump at a time when his administration is doling out billions of dollars in relief to companies.
In several states – most of them Republican-led – governors said they had seen signs that the coronavirus curve is flattening, making it possible to start reopening businesses and public spaces.
Georgia governor Brian Kemp announced plans to restart his state’s economy before the end of the week.
Mr Kemp said gyms, hair salons, bowling alleys and tattoo parlours could reopen on Friday, as long as owners followed strict social distancing and hygiene requirements.
Tennessee governor Bill Lee announced that businesses across most of the state would begin reopening as early as next week, although the order did not cover counties with the largest cities, including Nashville, Memphis, Knoxville and Chattanooga. Both states are led by Republicans.
Republican West Virginia governor Jim Justice said he would allow hospitals to begin performing elective procedures if the facilities met an unspecified set of criteria, while Democratic Colorado governor Jared Polis said he would let his statewide stay-at-home order expire next week as long as strict social distancing and other individual protective measures continued.
But governors from many other states said they lacked the testing supplies they need and warned they could be hit by a second wave of infections, given how people with no symptoms can still spread the disease.
Worldwide, the virus has infected nearly 2.5 million people and caused more than 170,000 deaths, according to a Johns Hopkins University count.
The US has been the hardest-hit country with more than 787,000 infections and more than 42,000 deaths.
The true figures are believed to be much higher, in part because of limited testing and difficulties in counting the dead.
There have been encouraging signs in places like New York state, where hospital admissions have levelled off. Monday’s death toll, at 478, was the lowest in three weeks, down from a peak of nearly 800.
Dr Anthony Fauci, the American government’s top infectious-disease expert, warned on ABC: “Unless we get the virus under control, the real recovery economically is not going to happen.”