MEXICO CITY—President Enrique Peña Nieto plans to raise income taxes on the wealthy in a bold move that seeks to make an unpopular extension of sales taxes to some food and medicines more palatable to the Mexican public, according to people familiar with the proposal.

Both measures would be part of a major tax overhaul intended to boost the coffers of a country with deep inequality and a decadeslong dependence on oil income, the people said.

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