MELISSA BLOCK, Host:
The Mexican president compares it to the Berlin wall. American sponsors call it essential for security. Either way, the U.S. appears to be on its way to building a 700 mile fence along the U.S./Mexico border. President Bush authorized it today by signing the Secure Fence Act of 2006.
GEORGE W: This bill will help protect the American people. This bill will make our borders more secure. It is an important step toward immigration reform.
BLOCK: The bill had strong bipartisan support in Congress but there are still some questions about when and whether the fence will actually be built.
From Tucson, NPR's Ted Robbins reports.
TED ROBBINS: First of all, this is not a story about whether a 700 mile fence will stop illegal immigration or even whether it's good public policy. It's about Congress telling the president look, we want you to build a fence.
JON KYL: And the fence is going to get built.
ROBBINS: Arizona Republican Senator Jon Kyl is certain of that. He talked with us at a campaign event.
KYL: The fence that we authorized, actually mandated, will be built over a period of years. Probably about half of it will be built within the first two or three years.
ROBBINS: But Colorado Republican Congressman Tom Tancredo, like Kyl a strong supporter of the fence, isn't that confident. We caught up with him as he was driving to his office in Denver.
TOM TANCREDO: The road is not clear to constructing the fence. It is probably better than 50-50, but it's no more than that.
ROBBINS: That's because there are plenty of obstacles, both political and physical, to building the wall.
The bill mandates five stretches of border fence, including a 370 mile stretch in California and Arizona traversing desert, mountain ranges, a national monument, two wildlife refuges and an Indian nation.
Look for the Indian tribe, whose lands will be split by the fence, to protest, along with the Mexican government and environmental groups. The Secure Fence Act actually exempts any terrain with more than 10 percent elevation so mountain ranges are out.
That leaves broad swaths of desert in Texas, New Mexico and areas near border towns like Naco, Arizona, where National Guard troops are already reinforcing existing single layer fencing.
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ROBBINS: And desert areas east of Naco, where the Minuteman Civil Defense Project is building a fence on private land. The Minutemen are still trying to raise money to complete their fence, which founder Chris Simcox says will be much like the government's.
CHRIS SIMCOX: Fiber optic fencing with steel mesh, double layered, security cameras. We can do it for $1 million a mile so the government ought to be able to do it for $1 million a mile.
ROBBINS: But government estimates range from $2 to more than $8 million a mile. That's where the political obstacles come in. Congress has already appropriated about $1.5 billion that can be used to start the fence. Future funding, maybe as much as $7 billion more, will have to come from future sessions of Congress and that worries Jon Kyl.
KYL: I'm not sure that if the Democrats are elected, they will pass the appropriation bills in the future to fund the construction of the fence. We have to do that each year.
ROBBINS: Lots of Democrats voted for the fence bill after saying all year that they didn't want it. Even the president has said he doesn't think a 700 mile fence is a good idea, but he signed the bill, which leads to the possible conclusion that the Secure Border Fence Act is all about election year politics, which is okay with Tom Tancredo.
TANCREDO: If it's done in order to - the timing of it is done simply for the purpose of helping out in the election, it's fine with me. I hope it does.
ROBBINS: Whether the fence actually gets built may be less important right now than whether the tough stance on border security translates into short term political security.
Ted Robbins, NPR News, Tucson.