have strained water-sharing arrangements with the US; the US has stepped up efforts to stem nationals from Mexico, Central America, and other parts of the world from illegally crossing the border with MexicoRefugees and internally displaced persons::IDPs: 12,000 (government's quashing of Zapatista uprising in 1994 in eastern Chiapas Region) (2004)Illicit drugs:illicit cultivation of opium poppy (c