The Tokyo-based company said Thursday the 5.6-centimetre-long fuel cell is the world's smallest of its type and can power an MP3 audio player for about 20 hours on a single charge of methanol fuel. 

Many companies are competing to develop fuel cells to power electronic gadgets in place of conventional batteries. Fuel cells produce electricity by converting hydrogen and oxygen into water and are widely considered power sources of the future because of their efficiency and low pollution. 

But manufacturers have faced difficulties in making them small and inexpensive. Toshiba said it was able to develop a system that allows a higher concentration of methanol while reducing the size of the fuel tank. 

But the 8.5-gram prototype currently produces only 100 milliwatts of electricity, and its output must be raised before it can be widely commercialized. Toshiba hopes to use fuel cells to power handheld electronic devices by 2005.