David Cameron has called on world leaders to deliver the "greatest possible pledge" of support to alleviate the suffering of Syrian refugees.
Opening an international conference in London, the Prime Minster said it was time for a "new approach" to the crisis.
He urged the 70 other nations at the talks to follow Britain, which has committed a further £1.2 billion over the next four years.
At the same time he called for assistance for Syria's neighbours - Turkey, Lebanon and Jordan - to enable them to open up job opportunities for the estimated 4.6 million refugees in their countries.
He also appealed for a commitment to ensure that all the refugee children in those countries had a school place by the end of 2016.
"If ever there was a moment to take a new approach to the humanitarian crisis in Syria surely it is now," Mr Cameron said.
"We are facing a critical shortfall in life-saving aid that is fatally holding back our humanitarian efforts.
"After years of conflict we are witnessing a desperate movement of humanity as hundreds of thousands of Syrians fear they have no alternative than to put their lives in the hands of evil people-smugglers in search of a future."