MONTERREY, Mexico — Standing in the baking sun outside the U.S. Consulate in Monterrey, hundreds of Mexicans wait anxiously for temporary work visas. But even before they were fingerprinted and interviewed for the permit, many had already paid recruiters thousands of dollars in hopes of easing the way.

Supplying the U.S. guest-worker program is a complex and sometimes criminal network of foreign recruiters who extort money from poor migrants and then keep them on the job by forcing them into debt or threatening their families back home.

Employers also are often at the recruiters' mercy, forced to accept workers who could be desperately in debt or simply wrong for the job.

And when their brief glimpse of the American dream becomes a nightmare, some legal guest workers simply disappear, melting into the growing U.S. population of illegal immigrants.

"Everyone has the same complaint. Everyone you see here is in debt," said Gilberto Escalante, a 41-year-old fisherman who swept his arm past at a crowd of migrant hopefuls waiting for visas outside the consulate in Monterrey.

"But there aren't any other options. The company calls the recruiter direct, and the recruiter has all the power."

All employers need to do to secure federal permission to hire foreign workers is provide proof that no American wants the job. Once that request is granted, companies rely on recruiters to do the rest, and the U.S. government stands back.

Critics argue the program desperately needs oversight and protections for both employers and workers, but demands for such an overhaul appear to have been ignored in the Senate's tentative immigration reform proposal.

Escalante, from the western Mexican fishing town of Topolobampo, spent $1,500 on fees and other expenses dictated by the recruiter before even beginning the visa process, which costs roughly $200 in consular fees if approved.

Once approved, he climbed aboard a bus dictated by the recruiter, which charged him $110 — double the going rate — to carry him to his sixth year working in the shrimp industry in Mississippi. There, he joined about 500 other foreign workers from Latin America and Vietnam.

Few file formal complaints or speak out against fraudulent practices. It's not worth risking the chance to earn more in an hour than many do in a full day of work in Mexico.

Todd Huizinga, a spokesman for the Monterrey consulate, said U.S. officials alert Mexican authorities when they become aware of suspicious activity, but described the recruiter process as a "private business."

"There is no U.S. law regulating recruiters," he said.

Some are legitimate and provide a valuable resource, charging a fair price for matching able-bodied foreigners to U.S. jobs. But in the absence of regulation and oversight, many overcharge migrants for handling visa applications, and some simply steal the migrants' money without ever doing the paperwork.

This happens on a global scale, but there is no recruiting network more powerful or vast than in Mexico, where the U.S. government issued 90,466 agricultural and other seasonal work visas in 2005 — 70 percent of the 129,327 handed out globally that year.

In a recent report, the Southern Poverty Law Center said migrants from Asia and Latin America have signed over the deeds to their homes and faced insurmountable debt and near slavery in return for the promise of a visa.

Guest workers who quit inside the United States face a range of sanctions, from losing any chance of returning as a legal guest worker to threats from recruiters.

Some are forced to sign blank promissory notes that can be filled out for any amount if they quit, enabling the recruiter to demand money or property from their families in payment.

Many U.S. employers want to eliminate the recruiters — who often charge the companies a fee as well — but can't because they don't speak Spanish and lack contacts in Mexico.

The AFL-CIO sees cross-border collective bargaining agreements as a solution to recruiter abuse, allowing them to alert employers to crooked recruiting practices and pressure them to use those who are honest.