"I would implore the international community not to be frozen waiting for the declaration," IRC President David Miliband told a virtual media briefing following a visit to the region.
He said only the United States had increased its financial support for East Africa, as the crisis in Ukraine has diverted donor cash.
"Elsewhere there is the great sucking sound of money coming out of East Africa," Miliband said.
Half of all deaths in Somalia's last famine, in 2011, occurred before famine was declared, he added.
Ethiopia, Kenya and Somalia are suffering their worst drought in 40 years, the region faces a fifth consecutive failed rainy season, and the United Nations has said it expects a famine to be declared in parts of Somalia before the end of the year.
East Africa's drought has been compounded by climate change and soaring global food prices, experts say.
The IRC estimates nine million cattle have died across the region while Baidoa, a southern Somali city, has seen its population soar as hunger-stricken families flee villages in search of food and water.
"In all the talk of net zero we can forget about ground zero," said Miliband, estimating that Somalia, Ethiopia and Kenya were responsible for just 1.2% of global greenhouse gas emissions while suffering massively from the effects of climate change.
Finance to help developing nations cope with the impact of climate change is being fiercely debated at the UN COP27 climate talks in Egypt, where delegates are trying to increase ambition on reducing planet-warming emissions.