WASHINGTON: The United States on Monday withdrew emergency use authorisations for two coronavirus treatments favoured by President Donald Trump, citing their lack of efficacy and safety concerns.

"It is no longer reasonable to believe that oral formulations of HCQ (hydroxychloroquine) and CQ (chloroquine) may be effective in treating Covid-19," Denise Hinton, chief scientist of the Food and Drug Administration (FDA) wrote in a letter.

She added: "Nor is it reasonable to believe that the known and potential benefits of these products outweigh their known and potential risk. "Accordingly, FDA revokes the EUA for emergency use of HCQ and CQ to treat Covid-19."