The situation in Italy and Spain, where infections and deaths have fallen in recent days, is "giving hope" on what the United States' "future could be", says Deborah Birx, one of President Trump's coronavirus advisers.
On Sunday, New York, the epicentre of the US outbreak, reported a drop in the number of new infections and deaths.
"We're hopeful over the next week that we'll see a stabilisation of cases in these metropolitan areas where the outbreak began several weeks ago," Dr Birx said.
The US has reported 337,274 confirmed infections and 9,619 deaths from Covid-19, by far the highest tally in the world.
On Sunday, Italy reported that 525 people had died in the previous 24 hours - the lowest daily figure since 19 March.
Another 674 people died in Spain - the lowest daily death toll in over a week.