The World Health Organization has warned on Monday that many countries are heading in the wrong direction in the fight against the novel coronavirus and the COVID-19 disease it causes, with sharp rises in their caseloads.

The organization, which is also known as the WHO, received reports of 230,000 new cases in a single day on Sunday, with almost 80 percent of those in 10 countries, and half in just two: the United States and Brazil.

The US reported 66,281 new cases on Sunday while Brazil reported 45,048, bringing their total cases to 3.16 million and 1.80 million, respectively.

The WHO's director-general, Tedros Adhanom Ghebreyesus, said during a virtual news conference from Geneva: "Let me be blunt, too many countries are headed in the wrong direction."

He said while the virus remains public enemy number one, the actions of many governments and people do not reflect this.

"Mixed messages from leaders are undermining the most critical ingredient of any response: trust," Tedros said, without naming countries.

President Donald Trump of the United States made headlines on Saturday for wearing a face mask in public for the first time since the start of the COVID-19 pandemic on a visit to the Walter Reed military hospital in Maryland, where he met wounded soldiers and healthcare workers.

Trump had previously said he would not wear a mask and mocked the Democratic Party's presidential contender, Joe Biden, for wearing one. But he claimed on Saturday: "I've never been against masks but I do believe they have a time and a place."

The White House has also been making concerted efforts to discredit Dr Anthony Fauci, the lead infectious disease expert in the US after Fauci became more vocal about his deep concerns about reopening the country amid a spike of cases.

In a statement on Saturday, a White House official told CNN that "several White House officials are concerned about the number of times Dr Fauci has been wrong on things". The words have been widely seen as a deflection from the sharp criticism of Trump and his administration's response to the pandemic.

On Monday, Tedros warned there will be dire consequences if governments do not clearly communicate with their citizens and roll out comprehensive strategies focused on suppressing transmission and saving lives. He said populations must follow basic public health principles of physical distancing, handwashing, mask-wearing, and coughing etiquette, as well as staying at home when sick.

"If the basics aren't followed, there is only one way this pandemic is going to go. It's going to get worse and worse and worse," Tedros said.

The WHO reported the outbreak is in an intense transmission phase across the Americas, South Asia, and several countries in Africa.

The epicenter of the virus remains in the Americas, where more than 50 percent of the world's cases have been recorded, Tedros said.

Maria Van Kerkhove, the COVID-19 technical lead at the WHO, said there is always the possibility of a resurgence of the virus in countries that have suppressed transmissions, but noted that what is important now is that many countries have used the time to build public health infrastructure and put their workforce in place as well as surveillance and other strategies.

They can "act fast when there is an upsurge in cases", she said.

Tedros emphasized that, no matter where a country is in its epidemic curve, it is never too late to take decisive action.

"I want to be straight with you: There will be no return to the 'old normal' for the foreseeable future," Tedros said.