The June 30 Front, which includes various groups including Tamarod -- a grassroots campaign behind Sunday's record protests against Islamist President Mohamed Morsi -- said it had delegated ElBaradei "to be the voice" of the opposition.
The Front "entrusts ElBaradei with the responsibility to ensure the execution of the Egyptian people's demands and to draft a scenario that aims at the complete implementation of the roadmap for the political transition," it said in an English-language statement.