Madagascar President Andry Rajoelina has said that tests will be carried out on a claimed plant-based "remedy" for the new coronavirus.
He has previously made claims about alternative treatments for the virus that have triggered words of caution from the UN's World Health Organization (WHO).
"On March 24, I received a letter saying that Madagascar possesses the remedy which could -- 'could' because it still has to be proved -- cure the coronavirus," Rajoelina said in a television programme late on Wednesday.
He said the letter claimed the plant could "completely cure coronavirus" but gave no details about the plant or the author of the letter.
Tests were being lined up and the country's scientists and laboratories were willing to take part, he said.
"We are going to carry out tests, and I am convinced that Madagascar will find this remedy," he said.
"We are going to change the history of the entire world."
Ninety-three people have been infected with the virus in Madagascar, according to official figures.
The pandemic has triggered a rush for herbal formulas, lemons and ginger in the belief that they can protect against the virus.
Rajoelina last month encouraged the use of alternative remedies as a way of "strengthening the antibodies" to coronavirus.
"We will make patient inhale ravintsara essential oils and provide them with high-calorie foods... in conjunction with medicine," he said then.
However, the UN's health body urged scepticism over claimed cures for COVID-19.
"The novel coronavirus is not a flu (and) ancient grandmother remedies must be seen with doubt," said WHO country representative Charlotte Faty Ndiaye.
On its website, the WHO says some medicines, including western and traditional ones, "may provide comfort and alleviate symptoms" of COVID-19.
However, "there is no evidence that current medicine can prevent or cure the disease" and people should not self-medicate, it says.
The US Centers for Disease Control (CDC), referring to claims for herbal or tea remedies, says: "There is no scientific evidence that any of these alternative remedies can prevent or cure the illness caused by COVID-19. In fact, some of them may not be safe to consume."