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.
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 testifying to a congressional committee examining the Trump administration’s response to the pandemic on May 6.
What’s the situation like in the US?
The United States alone has more than 1.3 million confirmed cases according to the Johns Hopkins University coronavirus tracker – almost six times as many as any other country.
The number of coronavirus-related deaths has now surpassed 80,000.
President Trump claimed that the US had “prevailed” in testing people for coronavirus infections in a news conference on Monday.
But as of this week, the US has tested only 2.75% of its 330m population, and no state has tested 10% of residents.
In a separate development, White House staff have been ordered to wear masks when entering the West Wing after two aides tested positive for coronavirus.
Mr Trump said he did not need to follow the directive as he kept “far away from everyone”.