President Donald Trump on Tuesday struck a sober note on the coronavirus pandemic as cases surge in the United States and his popularity sags, admitting that the situation could "get worse" and encouraging the public to wear masks.

"Some areas of our country are doing very well, others are doing less well. It will probably unfortunately get worse before it gets better," Trump said at his first press conference on the response to the pandemic that he has given since late April.

U.S. President DOnald Trump holds up his face mask during a press conference at the White House on July 21, 2020, in Washington. (Getty/Kyodo)

The remarks came after he had repeatedly downplayed the threat of the epidemic despite growing concerns over the spikes in cases across the country that were seen from June in the process of reopening the economy from the coronavirus-induced shutdown.

Trump even showed that he is carrying his own mask adorned with a presidential seal in his suit pocket, after spending months rejecting the use of masks, a practice recommended but not required by the country's health protection agency.

"We're asking everybody that when you are not able to socially distance wear a mask, get a mask. Whether you like the mask or not they have an impact," he said.

The Republican president has faced criticism that he should set an example for the public by using a mask to reduce the spread of the virus, rather than allowing the issue to remain politicized. Surveys suggest that the use of masks has become a divisive issue depending on an individual's political affiliation.

Trump finally wore a mask in public earlier this month during a visit to a military hospital and tweeted Monday that it is "Patriotic to wear a face mask when you can't socially distance."

The shift in Trump's tone over the pandemic came as his job approval ratings have continued to fall in recent months and national polls have showed him trail presumptive Democratic presidential nominee Joe Biden with little more than three months to go to the presidential election.

Trump repeated during the press conference his claim that China, where the virus was first detected late last year, should have stopped the disease at the source, while maintaining the upbeat outlook that vaccines are "coming a lot sooner than anyone thought possible."

But he acknowledged that he is "fully responsible" for the consequences of the outbreak, in stark contrast with his remarks in March in which he said he had no intention to "take responsibility at all" over delays in virus testing.

In the United States, more than 3 million people have been infected with the coronavirus and 140,000 have died, with both figures the highest in the world.