Given the task definition and input, reply with output. In this task, you need to translate the given English sentence to the French language

What will then be the most efficient body for decision-making on common security and defence issues -- the European Council or WEU?

Quelle sera alors l'instance de décision la plus efficace en matière de sécurité et de défense commune, le Conseil européen ou celui de l'UEO ?