The United States must also work with international organizations such as the United Nations High Commissioner for Refugees and the International Organization for Migration as well as the Mexican government to provide shelter and food to migrants on Mexico’s southern border. The Mexican government has said that Central American migrants in that area, as well as near the United States-Mexico border, can apply for Mexican work permits. At the same time, the United States should increase its funding to and engagement with the United Nations refugee agency to quickly expand Mexico’s ability to process refugee and asylum claims. This would be a major change for the Trump administration, which has been hesitant to work with many international organizations and which pulled out from the United Nations-brokered Global Compact on Migration before it was even finalized.Longer-term work is also essential to break the cycles of lawlessness and economic deprivation fueling migration.The United States should not be threatening to curtail assistance to the Northern Triangle countries, as President Trump has done. Instead, it should be providing additional assistance focused on job creation and strengthening anti-gang and violence prevention programs. Effective but small-scale local programs to combat these problems already exist — they should be expanded so their impact is felt across the region. The president-elect of Mexico, Andrés Manuel López Obrador, who will take office on Saturday, has spoken of his country playing a more active role in economic development in the Northern Triangle. The United States should leverage that interest to the fullest extent possible.Any effort to promote more stable, sustainable societies in the Northern Triangle must also include the region’s private sector, which should be pressed to contribute financially to American aid packages. And the United States should support efforts to root out corruption that is often fueled by predatory corporate interests. Instead of tough talk and empty gestures, it is time for the United States to provide leadership based on both our national interests and our values. If it is smart and open to working with others, the administration can manage the flow of migrants humanely and efficiently. If it is not, this crisis will only get worse. Roberta Jacobson was United States ambassador to Mexico from 2016 to 2018 and assistant secretary of state for Western Hemisphere affairs from 2012 to 2016. Dan Restrepo was special assistant for Western Hemisphere affairs for President Barack Obama from 2009 to 2012.Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram.