Among the obstacles for Trump’s mass deportation campaign are the countries refusing to take back their undocumented migrants.

President Donald Trump on Monday suggested sending repeat criminal offenders to foreign countries, suggesting the move may cut the government’s spending on prisons, following an escalation of arrests across the country in recent days as part of what Trump has promised would be the “largest deportation operation” in U.

Deportation flights between the U.S. and Colombia have resumed following a dispute between the two countries that nearly led to a trade war.

Colombian President Gustavo Petro announced that Colombia was suspending permission for previously authorized U.S. deportation flights to land in Colombia. Ostensibly driving Petro’s action were concerns that Colombian nationals were not being treated with respect during the deportation process because they were being transported by military aircraft.