The United Nations said on Tuesday it aimed to re-settle more than 450,000 Syrian refugees, about one-tenth of those now in neighboring countries, by the end of 2018, but conceded it needed to overcome widespread fear and political manipulation.

The U.N. refugee agency is urging countries worldwide to take in Syrians for resettlement as well as for humanitarian reasons of family reunification, medical treatment or scholarships to complete their studies.

More than 4.8 million Syrian refugees have fled to Turkey, Lebanon, Jordan and Egypt to escape a war that has killed more than 250,000 people since 2011 and left 13.5 million inside Syria in need of aid.