Leaders of four major cities have pledged to ban the use of all diesel vehicles from their roads by 2025.
Mayors of Paris, Madrid, Mexico City and Athens made the announcement at the C40 Summit in the Central American country in order to tackle air pollution in their regions.
They will incentivise the use of alternative vehicles and boost walking and cycling instead.
Around three million deaths are reported every year due to outdoor air pollution, according to the World Health Organisation (WHO).
The news follows C40’s report which suggests a $375 billion (£300bn) investment will be needed to end cities’ emissions growth by 2020.
Mayor of Paris, Anne Hidalgo said: “We stand up to say we no longer tolerate air pollution and the health problems and deaths it causes, particularly for our most vulnerable citizens. Big problems like air pollution require bold action and we call on car and bus manufacturers to join us.”
In the UK, Mayor of London Sadiq Khan has pledged to stop buying “dirty diesel” double decker buses.
Last month, Volkswagen said it will stop selling diesel cars in the US.