(CNN) Beto O'Rourke is set to visit Mexico on Sunday to meet with migrants in an effort to highlight the conditions facing those forced to wait outside the United States as they seek asylum.

The former Texas congressman will meet in Mexico with people who are seeking asylum, predominantly from the "Northern Triangle" countries of Guatemala, Honduras, and El Salvador, and are being forced to wait outside the country for the duration of their immigration proceedings under President Donald Trump's administration's "Remain in Mexico" program -- which O'Rourke's campaign said is "unlawful."

"In all of the debate around immigration, we can't forget who it impacts most: the people traveling thousands of miles, fleeing the worst kind of violence and oppression," O'Rourke said in a statement. "Turning away refugees, families and asylum seekers is not who we are as a country. But as long as Donald Trump is president -- it will be."

It's O'Rourke's first international trip as a Democratic presidential candidate, but to a city he has visited often: the bridge from Ciudad Juárez to El Paso is just five miles from O'Rourke's house, which overlooks Mexico.

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