EU foreign policy chief Catherine Ashton was set to address the General Debate of the 69th UN General Assembly on Wednesday.
Her speech comes after Hassan Rouhani blamed the rise of violent extremism on "certain states" and "intelligence agencies" and called for a regional solution to the increasing problem.
This year's General Debate comes as a US-led coalition has begun a campaign of air strikes targeting the Islamic State terrorist organization in Syria and Iraq.
Speakers will take the floor over the next week on the theme of the debate, “Delivering on and Implementing a Transformative Post-2015 Development Agenda” as well as urgent crises ranging from the ongoing conflicts in Syria, Iraq, Ukraine and South Sudan.
Among the high-level meetings are a Security Council summit Wednesday chaired by Obama, whose country holds the body’s presidency for the month, to draw international attention and action to the growing and dangerous phenomenon of foreign terrorist fighters; and a session convened by Secretary-General Ban Ki-moon for 25 September to focus on a more robust international response to Ebola crisis in West Africa