Sick children, families and businesses are among the many people in Haiti, a country plagued by gang violence, likely to be hit hard by a U.S. travel ban.

The Trump administration announced in a proclamation on Wednesday that it will ban nationals from Haiti from entering the United States and partially limit Cubans and Venezuelans from coming into the country.

An aid organization that has sent more than 100 Haitian children with serious cardiac conditions to the U.S. for heart surgery said President Donald Trump’s travel ban will stall or cancel lifesaving procedures.