U.S. authorities have approved a request from Liberia's government for sample doses of the experimental ZMapp drug to treat Liberian doctors infected with Ebola, the Liberian presidency said.

A statement on the Liberian presidency's website said the drug would be delivered to the West African country this week by a U.S. government representative, after a direct appeal to President Barack Obama on Friday by Liberian President Ellen Johnson Sirleaf.

However, a spokesperson for the U.S. Health and Human Services Department said U.S. authorities had simply assisted the Liberian government in contacting the drug's manufacturer.