But the choice of the nearby Texcoco lake bed has some opposition leaders up in arms. Amalia Garcia, president of the leftist Party of the Democratic Revolution, or P-R-D, says her main concern is the impact on the environment.

She says the construction at Texcoco would have a terrible impact on the ecology there and that the zone is also important for its aquifers. The old lake bed has also been used in controlling water flow and preventing floods in the city.

Environmental groups are also protesting the decision to build the airport at Texcoco, citing, among other concerns, the impact on migratory birds, including ducks and geese, that visit the area. Homero Aridjis, Mexico's best-known environmental leader, is planning to take the case before the North American Free Trade Agreement's Environmental Cooperation Commission. He notes that the migratory birds are mostly from Canada and the United States.

Fox administration officials, however, say Texcoco has many advantages over the other site studied for an airport, Tizayuca, in the state of Hidalgo, about 80 kilometers north of Mexico City. Besides being a lot farther from the capital, they say Tizayuca's nearby mountain terrain presented problems for air traffic controllers and pilots.

But the controversy over the Texcoco selection is already showing signs of escalating into violent confrontation at the proposed site. The government already owns most of the 15-thousand-hectare area, but it has issued expropriation orders for four thousand 500 more hectares. The people affected are mostly small subsistence farmers in the area and they are not happy. Protesters have occupied the streets in one town in the zone, forcing the mayor and other officials to leave.