WASHINGTON (AFP) - President Donald Trump, keen for an early lifting of economically costly social distancing measures against the coronavirus, said on Thursday (March 26) he would propose dividing the United States by risk levels.

In a letter to state governors released by the White House, Trump said that better testing now allows the mapping of virus threat on a local level.

"Under these data-driven criteria, we will suggest guidelines categorizing counties as high-risk, medium-risk, or low-risk," he said.

Trump said the new plans would be drawn up "in close coordination" with health experts.

He did not say when the new guidelines would be issued but he has previously indicated this will be as early as next week when a 15-day period recommending social distancing across the entire country will expire.

State governors have the authority to order or lift quarantines and social distancing measures, so it is not clear what response Trump's push for a quick return to normal will get.

Alarmed by the plunge in economic activity as large numbers of Americans stay away from their jobs and transport slows to a trickle, Trump has this week laid out the case for a rapid resumption of normal activity.

However, he walked back his initial push for a broad reopening of America by Easter - in less than three weeks - after criticism in Congress, the media and among some health professionals, who argue that patience is needed to take the momentum out of the coronavirus' spread.

Too early an end to social distancing could allow the disease to rebound, they warn.

Thursday's letter indicated that Trump is considering a flexible and limited reopening in areas of low risk, rather than a more widespread shift.

However there was little other detail in the message about how he sees it working.

"As we enhance protections against the virus, Americans across the country are hoping the day will soon arrive when they can resume their normal economic, social, and religious lives," he wrote.