GENEVA (Reuters) - The use of an experimental drug to treat two U.S. charity workers stricken by the deadly Ebola virus has prompted the World Health Organization to consider the implications of making such treatments more widely available, it said on Wednesday.

The Geneva-based agency, which is hosting a two-day Emergency Committee of experts to decide on the international response to the disease that has killed nearly 1,000 people in West Africa, said it would convene a meeting of medical ethics experts early next week.

"We are in an unusual situation in this outbreak. We have a disease with a high fatality rate without any proven treatment or vaccine," WHO Assistant Director-General Marie-Paule Kieny said in a statement.

"We need to ask the medical ethicists to give us guidance on what the responsible thing to do is."

The WHO statement said that the gold standard for assessing new medicine involved a series of trials in humans, starting small to make sure the medicine is safe to use, and the guiding principle was to "do no harm."

There is no registered medicine or vaccine against the virus, but there are several experimental options under development.

The treatment given to the two U.S. medical workers consists of proteins called monoclonal antibodies, or "plantibodies," that bind to and inactivate the Ebola virus and had only been tested in lab animals.

WHO has been criticized for a slow response to the outbreak, the most deadly and widespread in the almost four-decade history of the disease.

On Tuesday, three of the world's leading Ebola specialists called for experimental drugs and vaccines to be offered to sufferers and said a more robust international response was needed.

They said the WHO was "the only body with the necessary international authority" to allow such experimental treatments and it "must take on this greater leadership role."

Last month, one of the three experts, Jeremy Farrar, a professor of tropical medicine and director of The Wellcome Trust charity, told Reuters that at that stage "not a single individual has been offered anything beyond tepid sponging and 'we'll bury you nicely.'"

The death toll in the four West African countries hit by the disease stood at 932 by Aug. 4, out of a total of 1,711 cases.