Washington (AFP) US Secretary of Defense Mark Esper has demanded "action" by NATO against Turkey over their offensive in northern Syria. He will travel to Brussels next week to ask allies for "joint and individual diplomatic and economic measures," Esper said Monday. The "unacceptable invasion" of Turkey "undermined" the international mission in the fight against the jihadist militia Islamic State (IS) and led to the release of "many" prisoners of jihad.