Some envision a wall. Others, a fence - or even a "virtual" fence of cameras, lighting, and sensors along the US-Mexican border. Whatever form it will take, the US is discussing, planning, and, in some places, already building it - much to the fury and frustration of neighbors south of the border.
As Mexican President Vicente Fox prepares to meet Thursday with President Bush and Canada's new prime minister, Stephen Harper, in Cancún, the proposed 700-mile, $2.2 billion barrier is a major point of contention - not just for the US and Mexico, but for the US and the whole region.
Regional leaders - whose countries in 2004 received some $45 billion sent home from immigrants in the US - have met three times recently to discuss how best to oppose it.
"At a moment when relations between the US and Latin America are at their lowest point since the end of the cold war, this fence proposal is viewed as a terrible affront," says Michael Shifter, vice president of the Inter-American Dialogue, a Washington think tank.
"It is hard to imagine any other symbol that more strongly reinforces the image of the "ugly American" and is more sharply at odds with the "good neighbor" concept."
It's not just the barrier, but other issues as well in proposed US immigration reform legislation that irk regional leaders and caused hundreds of thousands of people to protest in multiple US cities over the past few days.
The US Congress passed a tough immigration bill in December that would make it a felony for illegal immigrants to be in the US, impose new penalties on employers who hire them, and erect a fence along one-third of the border's total length.
At present, just over 80 miles of federally enforced barriers and fencing are erected at strategic points on the border, mainly in Texas and California.
This week, the Senate will debate a comprehensive bill that is expected to include guest-worker provisions and avenues for legal residency, while at the same time beefing up border security. So far, a draft of the bill calls only for expanding and reinforcing fencing in Arizona - the border state with the most illegal immigration traffic - and adding 200 miles of vehicle barriers there, but more extensive fencing elsewhere is still under discussion.
"No country that is proud of itself should build walls," Fox told reporters when he last met Bush one year ago, and a month after the House began talks on approving a fence. "[I]t doesn't make any sense."
Since then, as the debate has continued in the US over what kind of fence is needed and where, Fox has called the proposal everything from "stupid" and "discriminatory" to "shameful," and heralded illegal migrants as "heroes" who will in any event find ways to cross the border.
Last year 1.2 million illegal immigrants were apprehended by the border patrol as they tried to cross into the US, and it is frequently estimated that close to the same number make it. Last year was also a record year for deaths. In 2005, 473 would-be immigrants died en route, many victims of thirst, heatstroke, exhaustion, or exposure when they tried to cross less carefully guarded desert areas.
Currently, 11.5 million to 12 million illegal immigrants live in the US, according to estimates in a report released this month by the Pew Hispanic Center. Of these, an estimated 6.2 million, or 56 percent, are Mexicans. Another 2.5 million, or 22 percent of the total, come from other Latin American countries.
The money these people send home is vital to the region's economy. In 2005, legal and illegal immigrants from Latin America and the Caribbean sent home $45 billion in remittances, double the total of a decade earlier, according to the Social Outlook 2005 report by the Economic Commission for Latin America and the Caribbean (ECLAC), a UN regional body. Mexican workers alone sent home a record $17 billion.
So while Fox might be the regional leader most concerned with, and vocal about, US immigration policy - he is far from the only one.
Spearheaded by Mexico, and galvanized by the fence proposals, foreign ministers and other top officials from Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama as well as Colombia, Ecuador, and the Dominican Republic met March 15 in Guatemala and vowed to coordinate their lobbying efforts against the US bill if it should pass in the Senate.
Guatemalan Vice President Eduardo Stein, in turn, called the bill "an affront to Latin America by a government that claims to be our partner, but which apparently only wants our money and our merchandise, and that sees our people as an epidemic."
This was the third time representatives from these 11 countries have gathered to discuss the US bill. In early January, they convened in Mexico City and put out a joint statement saying that "incomplete measures that only involve the stiffening of immigration policies do not represent an integral solution for dealing with the challenges posed by the phenomenon of migration."
In February, the group met again in Cartegena, Colombia, and devised a plan to identify key US senators to reach out to on the issue. Both the Mexican parliament and the five- nation Central American Parliament have condemned the proposed fence and are calling on the Senate to throw it out.
"Our message is that we are your neighbors, we are your friends. This is a common challenge," Carlos de Icaza, Mexico's ambassador to the US, told reporters in Washington last week. "And we are part of the solution, not only part of the problem."
• Ms. Harman is Latin America correspondent for the Monitor and USA Today.