Ayatollah Sistani says propagating Islam in non-Muslim countries is wajib (mandatory):

Religious Authority: 
Ali al-Sistanti
Fatwa Question or Essay Title: 
Ayatollah Sistani says propagating Islam in non-Muslim countries is wajib (mandatory):

Question: a person has the ability to propagate Islam to non-Muslims or to disseminate religious knowledge among Muslims in non-Muslim countries without any danger of losing his own faith, is it wajib on such a person to do propagation (tabligh)?

Fatwa: Yes, it is wajib kifa'i (a mandatory duty on for all Muslims) upon him and all the others who have the ability to propagate [Islam].