The United Nations launched its biggest ever humanitarian appeal for Syria on Thursday, seeking $8.4 billion after only securing about half the funding it asked for in 2014.The aid is desperately needed to provide help to 18 million people in both Syria and scattered through the region, as well as the countries and communities struggling to host them, UN officials told a donors' meeting in Germany.Some 200,000 people have died and nearly half the Syrian population has been displaced by the conflict that began with anti-government protests in 2011 and spiraled into full-scale civil war. The number of people needing humanitarian aid has increased by 2.9 million in just 10 months."We need a new aid architecture," said UN High Commissioner for Refugees Antonio Guterres."Syria's war is still escalating and the humanitarian situation is becoming protracted. Refugees and internally displaced people have exhausted their savings and resources and host countries are at breaking point."Syria's neighbors Lebanon, Turkey, Jordan and Iraq have been cutting back sharply on the number of Syrian refugees they allow to cross their borders as they can no longer cope with the influx, according to humanitarian agencies.