An additional £10m ($15m) will be provided by the UK for countries in West Africa facing the threat of drought, the government has announced.
Estimates suggest 1.5 million children in the Sahel region face starvation.
International Development Secretary Andrew Mitchell urged other nations to follow the example of the UK, which has already committed £10m to the crisis.
"Britain will not sit back while children starve to death in the Sahel," he added.
In January, Oxfam and Save the Children said thousands of people in East Africa died needlessly from famine last year because the international community failed to heed early warnings.
Mr Mitchell urged his counterparts around the world to take action against the latest threat.