The US's top infectious diseases doctor is to tell senators that the country will suffer "needless suffering and death" if it opens up too soon.
In an email to the New York Times, Dr Anthony Fauci set out the arguments he intends to make at Tuesday's hearing.
"If we skip over the checkpoints in the guidelines to Open America Again, then we risk the danger of multiple outbreaks," he told the newspaper.
More than 80,000 people have died from the coronavirus in the US.
Re-opening the country prematurely "will not only result in needless suffering and death, but would actually set us back on our quest to return to normal" said the doctor, who is a key member of the White House coronavirus task force.
In his comments to the New York Times, Dr Fauci was referring to the White House's Opening Up America Again plan, which includes three 14-day phases that states should consider implementing as they allow schools and businesses to re-open.
Witnesses will be appearing remotely. Three members of the White House coronavirus task force are self-isolating after possible exposure to the illness, including Dr Fauci.
Centers for Disease Control and Prevention director Dr Robert Redfield and Food and Drug Administration commissioner Stephen Hahn are also self-isolating.
Dr Fauci has tested negative but will continue to work from home for the time being, and will be regularly tested.
He plans to warn of the risks associated with reopening the country too soon, and will advise people that there is a lot they can do to get back to normality, but they should follow government guidelines, he told CBS News.
Some US states are beginning to lift lockdown orders. Georgia, Oklahoma, Alaska and South Carolina have already allowed some businesses to reopen and have issued plans that call for more rules to be relaxed.
Tuesday's hearing will be Dr Fauci's first appearance before lawmakers since President Donald Trump declared a state of national emergency in March.
The senior health adviser – who has become the public face of the fight against the virus in the US – was blocked from Read More – Source