A total of nine countries are yet to ratify the UNESCO International Convention against Doping in Sport after Sierra Leone became the latest country to sign it today.
The World Anti-Doping Agency (WADA) confirmed Sierra Leone were the 186th nation to abide by the Convention.
Five African countries - Guinea-Bissau, Mauritania, Sao Tome and Principe, South Sudan and Tanzania - have not signed it.
Afghanistan, Lebanon, Timor Leste in Asia and Niue in Oceania are the other nations who have not yet become signatories.
WADA have claimed 99 per cent of the world has now "pledged its support to clean sport" following the announcement that Sierra Leone had signed the convention.
Sierra Leone, the capital of which is Freetown, remains among the world's poorest countries.
"We are delighted that Sierra Leone has become the latest State Party to show its commitment to clean sport through its ratification of the UNESCO Convention," said WADA President Sir Craig Reedie.
"Ninety-nine per cent of the world has pledged its support to clean sport and vowed to ensure that the UNESCO Convention is implemented and practiced effectively in their respective countries.
"We are very pleased that Sierra Leone has joined them."
The Convention was adopted in October 2005 and is the practical instrument by which Governments formalise their commitment to the fight against doping.
Given that many Governments cannot be bound by a non-Governmental document such as the World Anti-Doping Code, the Convention allows them to align their domestic policies with the Code, thus harmonising the rules governing anti-doping in sport and public legislation.
Under UNESCO standards, the Convention has set records in terms of the speed with which it was prepared, adopted and ratified, it is claimed.