U.S. President Donald Trump said that under new proposed guidelines announced on Thursday some states could begin re-opening "literally tomorrow" and that 29 others could take that step "relatively soon."

The plan outlines how U.S. state governors could act to revive the U.S. economy from its coronavirus shutdown in a staggered, three-stage process.

Speaking at his daily briefing on the coronavirus, which has killed more than 32,600 Americans in a matter of weeks, Trump argued that a prolonged shutdown could be deeply harmful to the U.S. economy and society.

The new federal guidelines recommend that states record a 14-day "downward trajectory" in coronavirus cases before beginning a three-phase process of re-opening.

The document lays out Trump's plan for opening businesses in states across the country that have been ravaged by the pandemic and its economic impact even though the responsibility for such decisions lies with state, not federal, authorities.

Trump also warned that the U.S. could see a "flare up" of coronavirus cases in the fall but said the country would be better prepared for a second outbreak.

"We're going to be in a great position with everything we've done and everything we've learned," he said.