The World Health Organization (WHO) expressed concern about the rising number of new coronavirus cases in poor countries, even as many rich nations have begun emerging from lockdowns.
The global health body said on Wednesday that 106,000 new cases of infections of the novel coronavirus had been recorded in the past 24 hours, the most in a single day since the outbreak began in December.
"We still have a long way to go in this pandemic," WHO Director-General Tedros Adhanom Ghebreyesus told a news conference. "We are very concerned about rising cases in low- and middle-income countries."
The WHO has come under fire from United States President Donald Trump, who accuses it of having mishandled the outbreak and of favouring China, where the virus is believed to have emerged late last year.
This week Trump threatened to withdraw from the WHO and permanently withhold funding.
Tedros acknowledged receiving a letter from Trump, but declined to comment further.
Tedros said he was committed to accountability and would carry out a review into the response to the pandemic.
Tedros said he had long been looking for other sources of funding for the WHO, saying its $2.3bn budget was "very, very small" for a global agency, around that of a medium-sized hospital in the developed world.
In comments that could further annoy Trump, Ryan said people should avoid using the malaria medicine hydroxychloroquine to treat or prevent coronavirus infection, except as part of a clinical trial to study it.
Trump has said he is taking hydroxychloroquine to prevent coronavirus infection.
"At this stage, [neither] hydroxychloroquine nor chloroquine have been as yet found to be effective in the treatment of COVID-19 nor in the prophylaxis against coming down with the disease," Ryan said.
"In fact, the opposite, in that warnings have been issued by many authorities regarding the potential side effects of the drug."