The US could have prevented more deaths from coronavirus with earlier intervention from government and health officials to contain the spread of the virus, according to Donald Trump's infectious disease expert Anthony Fauci.

"I mean, obviously, you could logically say that if you had a process that was ongoing and you started mitigation earlier, you could have saved lives. Obviously. No one is going to deny that," Mr Fauci said in an interview on Sunday with CNN's Jake Tapper.

"But what goes into those kinds of decisions is complicated," Mr Fauci said, cautioning against coming down too harshly on government officials for how they responded to a complicated pandemic on which scientists had very little reliable data while they weighed other risks to shutting down the economy.

"But you're right. I mean obviously if we had right from the very beginning shut everything down, it may have been a little bit different. But there was a lot of pushback about shutting things down back then," Mr Fauci said.

By mid-day Sunday, more than 21,000 Americans had died from Covid-19. Officials have reported more than 525,000 cases. Both numbers are the highest of any country in the world, though some other countries have higher per capita death and infection rates.

Mr Fauci disagreed with Mr Tapper's notion that the US's ballooning number of confirmed cases of Covid-19 should be mostly attributed to its government not taking the coronavirus seriously enough in the crucial period from mid-February through mid-March, when the virus was first spreading in the US.

"It isn't as simple as that, Jake, I'm sorry, to just say, 'This is all happening because we got started too late,'" Mr Fauci said.

"Could you have done something a little bit earlier? Would it have had an impact? Obviously. But where we are right now is the result of a number of factors: the size of the country, the heterogeneity of the country," Mr Fauci said.

The New York Times reported over the weekend that Mr Fauci and other health officials had been trying to advise the president to begin advocating for preventive steps such as social distancing and partial shutdowns of the economy as early as the third week of February. Mr Trump didn't publicly endorse such steps until mid-March.

Meanwhile, Mr Trump has given his administration's response to the health crisis a perfect 10 out of 10 and recently downgraded the number of projected deaths from Covid-19 in the US to roughly 60,000, down from models that were predicting between 100,000 and 200,000 dead earlier this month.

“We’re going to win. We’re going to do it much sooner than people think," Mr Trump said at his daily coronavirus press briefing last Thursday, where he projected a strong bounce back by the US economy.

Mr Fauci said on Sunday that the US could begin loosening some of its economic shutdown and social distancing restrictions as early as "next month," a timeline that comports with Mr Trump's target date of 1 May for re-opening parts of the economy.

"We are hoping that at the end of the month we could look around and say, 'Okay, is there any element here that we can safely and cautiously start pulling back on?' If so, do it. If not, then just continue to hunker down," Mr Fauci said.