The U.N. refugee agency is launching an unprecedented appeal to the private sector to help pay for shelters for 2 million refugees worldwide amid a "huge shortfall in funds" for that purpose.

Spokesman Leo Dobbs says the appeal aims to tap philanthropists, companies, foundations and individuals as a potential source of new money because UNHCR hasn't gotten enough funds from its traditional government sources.

The "Nobody Left Outside" campaign aims to raise funds to build or improve shelter for 2 million refugees by 2018, or about one-eighth of the people UNHCR was helping in mid-2015. UNHCR says housing operations are expected to cost $724 million this year, but only $158 million is currently available.

UNHCR says 60 million people are forcibly displaced now, the highest figure since World War II.