"I say to-may-to, you say to-mah-to - let's call the whole thing off," the old song goes. And that's exactly what members of Congress may do with plans to reform obsolete immigration and labor laws if the Bush administration and Mexican leaders don't start singing off the same page concerning illegal immigrants.

To say immigration is a touchy matter is an understatement. In Mexico, freedom to work in the United States seems almost a birthright.

Yet, north of the Rio Grande River, immigration is a third rail of politics: Touch it and you get zapped, either by those who want to build a wall to keep immigrants out or by employers who want to let in as many "informal workers" as possible.

Mexican oligarchs see free movement of labor northward as a safety valve to relieve pressure from a million workers a year entering Mexico's labor force with no job prospects. Rather than liberalize their economy to end corrupt monopolies, strengthen property rights and establish the rule of law, they would rather keep things as they are and merely ship their jobless, poorly educated throngs north.

In Washington, security experts and diplomats view the apprehension of 1.5 million illegal migrants penetrating the U.S. border as a security issue. Drug traffickers and gang members are already part of the influx, so why not terrorists?

Moreover, the lack of a viable guest-worker program, along with tightening border controls, forces many migrant workers to stay and then smuggle in their families. Authorities in Southwestern states see them living on the margins, not paying taxes, overburdening public support programs and challenging law enforcement.

While many U.S. politicians wish the issue would go away, Mexico's political elites dream of a migration pact. But U.S. and Mexican economies and public institutions are too far out of sync for that to be realistic. Undeveloped capital markets in Mexico still make borrowing money difficult for small businesses. An inadequate education system prepares too few citizens for modern jobs. And despite 10 years of increasing commerce under the North American Free Trade Agreement, Mexico has been creating only 200,000 new jobs yearly.

In contrast, U.S. and Canadian economies and institutions are almost seamless. Central American countries have cooperated on defense and law enforcement for years. Although open borders with Mexico would require better military and police collaboration, old guard Mexican politicians say that would violate their sovereignty.

While it's good to look after one's own interests, U.S. and Mexican leaders have done little to facilitate understanding. Both the Gore and Bush campaigns of 2000 snubbed candidate Vicente Fox, thinking an opposition party candidate could never win. President Fox hasn't forgotten and has made little effort to see bilateral issues from Washington's side. His myopic first foreign secretary, Jorge Casteneda, talked him into pursuing an open-border treaty after September 11, 2001, just as George Bush's priority became keeping foreign terrorists out.

Mexico's latest volley is a comic book warning prospective immigrants of the dangers of crossing illegally - but giving them survival tips if they go. However well intended, its surprise revelation in the U.S. press suggests an uncooperative partner in controlling migrant flows. This is unfortunate, because Mexico needs to persuade Central American authorities to help control emigration from their jurisdictions.

Hundreds of miles distant from Washington and Mexico City, the actual U.S.-Mexican frontier stretches 2,000 miles, home to 14 paired cities and 12 million people. There, U.S. and Mexican citizens cross the line daily to commute to jobs in both countries, see relatives and facilitate trade that has grown to about $650 million daily.

Imposing draconian controls there would devastate the economies of both countries and still fail to staunch the flow of people willing to swim rivers and brave deserts to put bread on the table. Ironically, the only hope of opening borders to improve trade and labor mobility is to slow the immigrant tide.

To do that, U.S. and Mexican officials must tackle some difficult topics: better education for Mexicans, an end to state monopolies, a better climate for small businesses and investment, and modern law enforcement and defense institutions.

Mr. Fox campaigned for these things, but has been thwarted by opposition officials who think he should keep sending Mexico's problems north. Those deputies fail to understand labor mobility can't exist without economies and public institutions that work harmoniously on both sides of the border.

Stephen Johnson is senior policy analyst for Latin America in the Davis Institute for International Studies at The Heritage Foundation.