After speaking about the need to "act now" against Islamic State militants at a United Nations Security Council meeting on Wednesday night, British Prime Minister David Cameron addressed the 69th General Assembly. Like many world leaders before him, Cameron centered his speech on the rise of Islamic State militants across the Middle East. Tweets from https://twitter.com/Jerusalem_Post/lists/un-general-assembly 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.Recounting the jihadist group's latest atrocities -- from their beheadings to abductions to mass killings -- against those who refuse to align with what he called the group's "sick extremist worldview," Cameron said the threat they pose was not confined to the Middle East, but was an international problem. Their murderous plans go well beyond the borders of Iraq and Syria, he said. The prime minister referred to the organization's successful recruitment methods and mounting influence across Europe, telling the 193-member assembly that Islamic State "affects us all," and must be tackled on a global scale. Alluding to the wars in Iraq and Afghanistan, which he termed "past mistakes," he said they should not hold the international community back, but rather lead to action. Pinpointing the root cause of the rise of Islamic State -- extremism -- he said the world faced an intellectual "war of ideas," and not only a military one. A recurring theme in his speech was the need for countries to work together including with Iran. He welcomed the Arab countries who have already signed on to the US-led coalition and said the Islamic Republic deserved an opportunity to participate. He referenced his first meeting with President Hassan Rouhani earlier on Wednesday and said there was room for Iranian engagement. To defeat Islamic State the world had to counter its "poisonous ideology," which, he noted, had nothing to do with Islam. Non-violent extremism had to be confronted as well -- namely the omnipresence of IS online and the hijacking of religion by militants.Extremist groups and insurgencies sprung up when people lost hope, he said, turning to Iraq, as he called for backing an inclusive government that will bring together all Iraqi factions.Moving on to Syria, he completely ruled out cooperation with President Bashar Assad in this fight, saying, "Our enemies’ enemy is not our friend. It is another enemy." Britain should join the US-led coalition uniting against the group, he said, adding that it was time to begin a new phase of action. He called on his parliament to move forward and OK plans to join air strikes against Islamic State in Iraq.