MARRAKECH, Morocco (AP) — Top U.N. officials and government leaders from about 150 countries are uniting around an agreement on migration, while finding themselves on the defensive about the non-binding deal amid criticism and a walkout from the United States and some other countries.

The Global Compact for Migration has proven a test for globally minded policymakers who want to ensure safe and orderly migration of people displaced by issues like war, economic necessity and climate change.

They have run into stiff political headwinds, mostly in parts of the West that want national borders to remain sacrosanct.

German Chancellor Angela Merkel joins U.N. Secretary-General Antonio Guterres among the biggest names in Marrakech for the two-day conference that is set to agree, but not sign, the compact by acclamation shortly after the opening Monday.