The tiny Pacific island state of Tuvalu has said it wants all its energy to come from renewable sources by 2020.
Public Utilities Minister Kausea Natano said his nation of 12,000 people wanted to set an example to others.
Tuvalu is made up of a string of atolls with the highest point only 4.5m (15 ft) above sea level, making it extremely vulnerable to flooding.
The government hopes to use wind and solar power to generate electricity, instead of imported diesel.
"We look forward to the day when our nation offers an example to all - powered entirely by natural resources such as the sun and the wind," Kausea Natano said.
Tuvalu and many other low-lying atolls in the Pacific, the Caribbean and the Indian Ocean fear that global warning could lead to sea level rises that could literally wipe them off the map.
Other nations - including Norway, New Zealand, Iceland and Costa Rica - have also vowed to become carbon neutral, reducing their emissions of greenhouse gases to zero.
Most of these countries have relatively small populations, and their pledges are unlikely to make a significant difference in the overall battle against global warming.
But many environmentalists say their stance is nevertheless important, as they provide a lead for other countries to follow.
"In a sense, they are paving the way for medium and larger economies which have to move if we are going combat climate change," Nick Nuttall, spokesman for the United Nations Environment Programme, told the French news agency AFP.
Tuvalu estimates it would will cost about $20m to generate all its electricity by using renewables. It has already begun the process by installing a $410,000 solar system on the roof of the main soccer stadium in the capital, Funafuti.