More than 40 developing nations on the front lines of climate change have pledged to pursue 100 percent renewable energy.

The Maldives, the Marshall Islands and other small island nations threatened by rising seas, drought-hit African countries and low-lying nations such as Bangladesh were among those who backed the declaration at U.N. climate talks on Friday.

Signatories said they will try to produce all their energy from renewable sources "as rapidly as possible."

Many of them that would require support from richer countries to switch to renewable energy. Some countries like Bangladesh are planning to expand coal power, a key source of global warming emissions, to meet their growing energy needs.

U.N. climate chief Patricia Espinosa applauded the initiative as a model of "political will" at a crucial time.