"The catastrophe is already upon us," Mueller said in an interview with the German newspaper Passauer Neue Presse, published on Saturday. He pointed to dire conditions in countries such as Kenya, Somalia, South Sudan and Ethiopia.
Mueller said the United Nations estimated the financial needs in eastern Africa alone amounted to $4 billion to $5 billion.
Creating a fund that would be continually restocked would make it easier to respond to recurring humanitarian crises, he said.
"We need to accomplish this as a world community," he said.
Ethiopia, for example, will run out of emergency food aid for 7.8 million people hit by severe drought by the end of this month, the Ethiopian government and humanitarian groups have said.
The United Nations said in March that more than 20 million people risk dying from starvation because of drought and conflict in Yemen, Somalia, South Sudan and northeast Nigeria, while more than 100 million face acute malnutrition worldwide.
Famine was declared in some areas of South Sudan in February - the first official famine in six years.
Mueller spoke ahead of a conference in Berlin on Monday that Germany is hosting to call more attention to Africa during its presidency of the Group of 20 industrialised countries.
Five countries - Ivory Coast, Morocco, Rwanda, Senegal and Tunisia - have already signed up for enhanced partnership agreements with G20 countries under a new "Compact with Africa" programme.
It focuses on finding private investors in areas such as energy production, agriculture and tourism. Ghana and Ethiopia have expressed interest in such partnerships, according to German officials.
Germany - which has taken in more than a million migrants over the last two years - is pressing for industrialised countries to work to avert another massive refugee crisis, given growing economic and climate-related challenges in Africa.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)