The number of cases of coronavirus in the United States has reached almost 800,000.
The US accounts for almost one third of the world's cases.
The world's tally has almost reached 2.5 million, while more than 170,000 people have died of Covid-19.
Mike Ryan, from the World Health Organisation, says lifting restrictions too early could be disastrous.
"Transitioning away from these measures means there is always the chance that the disease will rebound.
"We need to move away from these lockdowns, but we need to not move away from lockdown - we need to move towards something else.
"Moving away from a bad thing or something that was necessary and has caused so much hardship for people is a good thing.
"But if you don't move towards something else you may be back exactly where you started."
