Trump said the new testing abilities would allow his administration to identify "high-risk, medium-risk and low-risk" counties. And those new guidelines will assist governors and other officials in deciding on "maintaining, increasing or relaxing social distancing and other mitigation measures they have put in place."
The president said that by doing "robust surveillance testing," officials will be able to "monitor the spread of the virus throughout the country."
Public health experts have said easing restrictions too soon could overburden hospitals and lead to more deaths and economic damage related to the virus.
Although the president said in the letter that "there is still a long battle ahead," Trump said Tuesday he wants the country back to business by April 12, Easter Sunday, even though his own public health officials have warned that the outbreak will get worse.
The number of reported coronavirus-linked deaths in the U.S. passed 1,000 on Thursday morning, according to an NBC News count. More than 68,000 cases have been reported nationwide, Johns Hopkins University said.
Many states have issued stay-at-home orders, closed schools and imposed strict policies, such as closing all nonessential businesses and aggressive social distancing measures, to mitigate the infection rate and avoid overwhelming hospitals.
The governors of Michigan, Indiana, Oregon and West Virginia issued stay-at-home orders Monday. Massachusetts Gov. Charlie Baker announced a stay-at-home "advisory" Monday. California, Illinois, New Jersey, New York and Pennsylvania are among the other states implementing sweeping mandates.
States are also looking to the federal government for critical help.
Trump has declared disasters in New York, California, Washington, Louisiana, Iowa, Florida, Texas and Illinois due to the coronavirus outbreak. Connecticut on Thursday joined the growing list of states that have asked the Federal Emergency Management Agency for a disaster declaration to cope with the "severity and magnitude" of the coronavirus outbreak.
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Although governors and local officials have the authority to lift their mandates, Trump has been eager for American life to get back to normal and regain the strong economy his administration boasted before the outbreak. However, some state lawmakers have resisted the calls.
New York Gov. Andrew Cuomo strongly criticized Trump's effort, saying Tuesday that "we will not put a dollar figure on human life."
"We can have a public health strategy that is consistent with an economic one," he said in a tweet. "No one should be talking about social Darwinism for the sake of the stock market."
Cuomo, a Democrat, has also been critical of the massive $2 trillion relief package, which Trump praised and which passed the Senate late Wednesday. The governor called it a "shortfall" compared to the funding relief the state needs.