Fauci says no guarantee US will have effective COVID-19 vaccine, warns spread 'could get very bad'

Fauci, however, cautioned that "there is no guarantee ... we'll have a safe and effective vaccine," and he urged Americans to come together to contain the virus.

Fauci warned that the daily increase of new cases in the United States, currently around 40,000, could reach 100,000 if people do not adhere to social distancing guidelines and wear masks.

"I am very concerned because it could get very bad," he said.

His remarks dovetailed with warnings by health officials that some Americans, particularly younger adults, have let down their guard since the end of mandatory lockdowns put in place in March and April to stop the pandemic.

Many states where the virus is now surging began reopening businesses without having met government health benchmarks for doing so safely.

There are fears the recent spike in cases could become turbo-charged later this week by the July 4 Independence Day celebrations, when Americans traditionally flock to beaches and campgrounds and gather to watch fireworks displays.

More than 126,000 Americans have died from COVID-19 and millions have lost their jobs as businesses and schools shut to contain the virus' spread. The economy contracted sharply in the first quarter and is expected to crater in the April-June period.

COVID-19 cases more than doubled in June in at least 10 US states, including Texas and Florida, a Reuters tally showed.

Los Angeles, the second-largest US city, has become a new epicenter in the pandemic as coronavirus cases and hospitalizations surge there despite California Governor Gavin Newsom's orders requiring bars to close and residents to wear masks in nearly all public spaces.

Los Angeles County reported nearly 3,000 new cases on Monday.

Another hot spot is Texas, one of the states that reopened its economy the earliest. On Tuesday, Governor Greg Abbott expanded his order hospitals in certain counties to cancel elective procedures so that bed space remains available for severe COVID-19 cases.

'HISTORIC MISMANAGEMENT'

The setback has dimmed hopes that the worst of the human and economic pain had passed for the country and renewed criticism of US President Donald Trump's handling of the crisis less than five months before he seeks re-election.

Democratic presidential candidate Joe Biden later on Tuesday will launch a fresh attack on Trump's "historic mismanagement" of the pandemic, said an aide who previewed his speech and who spoke on condition of anonymity.

Biden will argue that earlier action by Trump would have reduced the number who fell ill and the economic impact of the virus.

Extraordinary measures have been taken to brace the economy, with Congress allocating nearly $3 trillion in aid to businesses and individuals and the Federal Reserve slashing interest rates, ramping up bond purchases and unveiling programs to backstop and extend corporate credit and promote lending.

Fed Chair Jerome Powell and US Treasury Secretary Steven Mnuchin are expected to be grilled about the effectiveness of the relief effort when they testify before a US House of Representatives committee later on Tuesday.