A cluster of migrants, grimy from the road and sweating in the searing heat, wait out the day about 500 yards from the border. They talk in nervous tones about border patrols, unscrupulous migrant smugglers, and finding work once they make it to the United States.
Miguel Gallo says his financial situation is so hopeless, he's more afraid of failure than he is of dying. "I've got seven children and a wife. If I don't make it, they're not going to survive."
The drama of illegal migration - the hopes that fuel it, the enormous personal risks for those who try - is familiar to most Americans, especially as Congress debates granting amnesty to the 3 million Mexicans working illegally in the US.
But Mr. Gallo and his companions aren't at the US-Mexico border. They're Central Americans in Tecun Uman, Guatemala, harboring the same dream of a life in the US that motivates many Mexicans - a dream that has just grown more distant.
On July 20, the Mexican government began a campaign called Plan Sur to stem the tide of Central American migrants. Analysts say it's a bargaining chip ahead of President Vicente Fox's September trip to Washington: We slow the flow of Central American migrants, you grant easier access to our workers. Both countries hope the outlines of an immigration deal will be agreed upon by Mr. Fox and President Bush at the meeting. "Stopping migration in the south is, of course, a gesture to the United States," says Manuel Angel Castillo, who studies migration at the Colegio de Mexico in Mexico City.
"What does the US get in return? Well, we can transform Mexico into the vast guardian of the southern border," says the Rev. Florencio Maria, who runs the Bethlehem Shelter for Central American Migrants in Tapachula, Chiapas state.
Authorities here publicly deny that's the rationale, since many Mexicans think it would be hypocritical to deny Central Americans something that Mexico wants for its own people. "We're trying to catch them because it's good for Mexico," says Felipe de Jesus Preciado Coronado, commissioner of the government's National Migration Institute, which is supervising Plan Sur. "But I also know very well that our efforts are of great benefit to the US."
Analysts estimate that thousands of troops have been sent south to Chiapas and Oaxaca states. Captured migrants are now flown back to their countries of origin, rather than dumped in Guatemala.
The plan has scored early victories, and Fr. Maria estimates 35 percent fewer migrants have passed through his shelter since July. Migrants say that smugglers, or coyotes, have increased their fees by as much as $1,000 to $3,500 per person.
Mexico deported 100,000 Central Americans in the first half of the year, and the number for the second half will far exceed that, predicts Mr. Preciado Coronado.
Maria suspects immigrants are taking more dangerous routes through the mountains instead of the coastal plains. "Fox is falling into the same trap the US fell into. Militarization won't cut migration, it will only make it more hazardous," he says.
As migrants cross 1,500 miles of Mexican territory before reaching the US, they become easy prey to corrupt cops and gangs that specialize in stealing from them.
"Mexicans at the US border say the hard part is about to begin. Central Americans at the US border say the hard part is over," says Mr. Castillo.
Tony and Roberto Leon sighed relief when they crossed the jungle border with Chiapas on Aug. 10, and beat patrols by hopping onto a freight train. The Honduran brothers expected an easy pull up the Pacific coast to Tijuana until a fellow migrant in their train car, waving a machete, demanded money. The brothers steeled themselves and hurtled out into the darkness, landing in grass. They made it back on foot to the Bethlehem Shelter, about 20 miles from Guatemala. Despite the scare, they say they'll try again soon.
Officially, 136 Central Americans died crossing Mexico last year, but Maria suspects many more deaths go unreported.
Ironically, the southern border itself is the easiest part. The official bridge that separates Tecun Uman from Ciudad Hidalgo, Mexico, is a good vantage point to watch the hundreds of makeshift ferries - truck inner-tubes with wooden slats lashed to them - that cross every day. Mexican officials at the border ignore them.
That soon changes. About 5 miles into Mexico, military checks begin. Buses are now being stopped about once an hour. The focus is the 150-mile-wide Isthmus of Tehuantepac, well inside Mexico. "It's a bottleneck, so it's much more efficient to work there than in the jungle on the border," says Preciado Coronado.
Migrants say they continue to come because the possible rewards outweigh any risk. Wages in most Central American countries are $3 a day. If they can make it to the US, they expect to make at least $40 a day. "There are people that want us, all we have to do is get there," says Jose Luis, a Guatemalan. "The only thing that's going to stop me now is if they put a factory in Mezatenango," his hometown, "and pay US wages."