Agency officials have told Congress they would prefer 300 to 400 miles of fencing in areas where they believe it would be effective, and latitude to employ other security methods elsewhere.
"In urban areas, we've found that fencing is very effective; but in rural areas, sensors and other technology are more effective," said Homeland Security spokesman Russ Knocke.
For The Record
Los Angeles Times Monday October 30, 2006 Home Edition Main News Part A Page 2 National Desk 1 inches; 37 words Type of Material: Correction
Border fence law: A map of the U.S.-Mexico border in Friday's Section A, accompanying an article about President Bush's signing of a bill authorizing fencing there, should have had a scale of 100 miles, not five miles.
The new law has encountered resistance in parts of the Southwest: Opponents include the Texas Border Sheriffs' Assn. and the city of El Paso.
Maria Luisa O'Connell, president of the Phoenix-based Border Trade Alliance, expressed concerns Thursday about the economic impact of more border fencing.
Mexicans who cross the border legally to shop in the U.S. "are seeing the fence as a sign that we don't want anyone to come in," said O'Connell, whose nonpartisan group works to stimulate cross-border commerce. "You want to have security, but you need a balance of economic security."
Many Democratic lawmakers have expressed skepticism about the effectiveness of more fencing in significantly reducing illegal immigration. They also said Thursday's bill signing spotlighted the GOP's failure to reach a consensus on other immigration-related issues.
"The president and this Congress had a historic opportunity to pass a tough but fair immigration reform plan this year, but instead that chance was squandered," said Sen. Edward M. Kennedy (D-Mass.).
The bill mandates that Homeland Security establish "operational control" of the border in 18 months, although it does not precisely define that term. It also calls for the agency to study potential improvements to the Canadian border.
Times staff writer Hector Tobar in Mexico City contributed to this report.
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The fence bill that became law Thursday is the most tangible result of a public debate that sparked large protests in several U.S. cities and dominated much of this year's congressional session.
The House passed a bill in December with a provision that would have made illegal immigration a felony. Strong opposition to that provision among Latinos helped attract an estimated 1 million people to a rally in downtown Los Angeles in early March; similar demonstrations occurred elsewhere.
In mid-May, President Bush took center stage with a prime-time speech calling for a path to U.S. citizenship for many illegal immigrants and a guest worker program.
The Senate passed a bill following that approach. But House Republican leaders expressed little interest in it. Congress settled on passing the fence bill in late September. The House approved it 283 to 138; the Senate vote was 80 to 19.