e Arizona desert for 3 days, rests at a migrant shelter in Nogales, Mexico, Thursday, April 6, 2006. Illegal migrants are rushing to the Arizona border, encouraged by the prospect of a guest-worker program in the U.S. and anticipating a toughening of border security that would make a dangerous journey even more perilous. (AP Photo/Dario Lopez-Mills)

He said the couple would rest for a few days, then try again, a plan echoed by dozens reclining on rickety bunk beds and carpets tossed on the floor after risking violent bandits and the harsh desert in unsuccessful attempts to get into the United States.

The shelter's manager, Francisco Loureiro, said he has not seen such a rush of migrants since 1986, when the United States allowed 2.6 million illegal residents to get American citizenship.

This time, the draw is a bill before the U.S. Senate that could legalize some of the 11 million people now illegally in the United States while tightening border security. Migrants are hurrying to cross over in time to qualify for a possible guest-worker program — and before the journey becomes even harder.

"Every time there is talk in the north of legalizing migrants, people get their hopes up, but they don't realize how hard it will be to cross," Loureiro said.

South-central Arizona is the busiest migrant-smuggling area, and detentions by the U.S. Border Patrol there are up more than 26 percent this fiscal year — 105,803 since Oct. 1, compared with 78,024 for the same period a year ago. Along the entire border, arrests are up 9 percent.

Maria Valencia, a spokeswoman for U.S. Customs and Border Protection, said the rise in detentions did not necessarily mean more people were crossing. She attributed at least some of the additional detentions to an increase in the number of Border Patrol agents.

"We've sent more technology and agents there, and I think that's had an impact," she said.

But Loureiro, who has managed the shelter for 24 years, said the debate in the U.S. Congress has triggered a surge in migrants. In March, 2,000 migrants stayed at the shelter — 500 more than last year.

Many migrants said they were being encouraged to come now by relatives living in the United States.

One of them is Ramirez, a 30-year-old who earned about $80 a week at a rebar factory in Mexico's central state of Michoacan.

He spent an entire night walking through the Arizona desert with his wife, Edith Mondragon, 29. When her legs cramped, their guide abandoned them and the couple turned themselves in to U.S. authorities. They were deported.

But they said they would try again when they regained their strength.

"We want to try our luck up there," Mondragon said. "We can't go back to Michoacan because there is no future there."

Ramirez said the draw was not only the prospect of work in Minnesota, where two of his brothers milk cows on a ranch. He was also excited about the idea he might be able to do it legally.

"My brothers said there is plenty of work there, and that it looks like they will start giving (work) permits," he said.

Many of the migrants also are being driven by a desire to get into the United States before the likelihood that lawmakers further fortify the border.

Since the United States tightened security at the main crossing points in Texas and California in the 1990s, hundreds of thousands of migrants have turned to the hard-to-patrol, mesquite-covered Arizona desert, risking rape, robbery and murder at the hands of gangs and now facing armed U.S. civilian groups.

About 2,000 people a day pass through Sasabe, a hamlet of just a few dozen houses and a Western Union office west of Nogales, says Grupo Beta, a Mexican government-sponsored group that tries to discourage migrants from crossing the border and helps people stranded in the desert.

On a recent afternoon, at least 40 vans overflowing with migrants arrived in the desert near Sasabe in less than an hour. Migrants and their smugglers waited for nightfall before starting a desert trek that would involve up to a week of walking in baking heat during the day and biting cold at night.

Grupo Beta agent Miguel Martinez mans a checkpoint 20 miles south of Sasabe, where he warns of the dangers of the desert, such as bandits armed with knives or guns who order migrants to strip naked, rob them and sometimes rape them.

He also tells about the volunteer border-watch groups that have sprung up in Arizona.

"Right now there are migrant hunters who are armed, and you should be careful," Martinez told a group traveling in a rickety van missing some of its windows.

At Grupo Beta's office in Nogales, Raul Gonzalez, 44, said he walked in the Arizona desert for five days before turning himself in when the blisters on his feet started bleeding and his left leg swelled up.

Like most migrants interviewed for this story, Gonzalez said he was robbed at gunpoint just after crossing into the United States.

"The guides and the robbers are all the same," he said.

Gonzalez said the first time he sneaked into the United States, he did it through Tijuana, across the border from San Diego. He said he worked illegally at a printing shop in Chicago for 15 years but got homesick before he could settle the paperwork for legal residence.

Despite the robbery and his failed trek, Gonzalez said he would try again once his feet heal. His bricklayer's salary of about $60 a week in the western state of Jalisco simply is not enough to provide for his four children.

"It's hard to cross," he said. "But it's harder to see your children have little to eat."