The plan was developed over many months and included a request from Mexico that the United Nations High Commissioner for Refugees establish shelters along its border with Central American, a senior administration official told Fox News. The goal is to provide humanitarian aid to members of the caravan, and either prevent them from entering Mexico, or process them individually as refugees or as legal entrants.

Mexico has also agreed to take back any migrant who evades their processing system and makes it to the United States. In the past, the U.S. has been required to house those who crossed the border illegally until their cases could be heard, and only after could they return them to their country.

“Just today, the Mexican government, and this is a very important step, requested the intervention of the U.N., the Office of the High Commissioner on Refugees, to help Mexico review any asylum claims from the members of the caravan,” Mexican Ambassador to the U.S. Geronimo Gutierrez told Fox Thursday night as he explained the situation.