IT is a rare encounter between the hunter and the hunted. On one side of the border fence - which is trampled and mutilated by the endless northward flow of illegal immigrants - hundreds of hopeful migrants wait restlessly for the sun to sink below the horizon.
Looking through the fence links from the other side, US Border Patrol officer J.D. Oliver speaks with frankness - and frustration - about the United States's inability to stop the flood.
``We haven't stopped anybody since I got here four years ago,'' says the tall, dusty-haired Texan. ``It's a joke.''
Mr. Oliver explains that the Border Patrol detained around 1.8 million illegal aliens last year. But by law he says, almost all of them had to be released back across the border within hours, where they would try to cross again - sometimes on the same night.
Turning to several dozen immigrants straining to hear the conversation, he remarks in Spanish: ``You know, they pay me $36,000 a year to stand here like a fool.'' Laughter erupts.
As Oliver holds court, five all-terrain vehicles shoot up the dirt road, forcing back immigrants who had gravitated to the US side of the border. Then in a display of mobility, the miniature dune buggies clamber up and down the steep river embankment.
``Sure it looks good,'' says Oliver. ``But you think any of these [illegal immigrants] is scared of our equipment?''
He stopped to survey the swelling crowd of immigrants. They have all come through this river levee, known as ``El Bordo,'' because it is only a five-minute sprint from the twinkling lights, and relative safety, of San Ysidro, California. Immigration experts estimate that the border patrol detains one of every three crossing immigrants - but not here.
``Do you think we're going to catch 30 percent of these people?'' Oliver asks. ``No way.'' He holds out his hands. ``Not when this is all I've got.''
If Congress were serious about clamping down on the border, Oliver says, it would have to let the Border Patrol use rubber bullets, tear gas, stun guns, even land mines.
``Congress spent seven years debating [the 1986 immigration law],'' says Oliver. ``We spent $4 billion implementing it. But it doesn't make any difference.''
As if to show just how easy it is to elude the Border Patrol, one taunting Mexican teenager cuts through the no man's land and swaggers past the Border Patrol agents to rejoin the crowd. Oliver shakes his head and shouts sarcastically: ``You're real cool, kid.''
When the sun touches the horizon, the brief interlude ends and the nightly ritual begins. Oliver leaves to get ready for the onslaught. And the immigrants, following their guides in groups of anywhere from five to 30, head off into the night - and into the US.