Expectations are high that the United States and Mexico will officially announce a guest worker temporary visa in scheme to coincide with the state visit of Mexican President Vicente Fox to Washington September 5-7. The program would give temporary legal status to tens of thousands of undocumented Mexican citizens currently working in the United States.

Mexico cannot begin to support all the workers who migrate northwards within its own creaking economy. While the United States does need large supplies of cheap unskilled labor in a number of key sectors, especially agriculture.

Mexican National Security Advisor Adolfo Aguilar Zinser says that at long last both countries have stopped trading accusations and are working together on this challenging issue.

"We have our own responsibilities to these people," he says. "You in the United States, and we in Mexico, because we are partners, we are neighbors, and our destinies are tied together. And destinies are people."

A considerable amount of ground work has already been done on the temporary worker visa scheme, including meetings between Mr. Aguilar Zinser, the Mexican Interior Minister, the Mexican Attorney General and their counterparts from the US side.

But practical problems still remain. Pedro Javier Gonzalez, who is Director General of the Mexican Institute of Political Studies, explains that the newly legalized status of tens of thousands of Mexican migrant workers will oblige the United States to pay for a whole range of resulting statutory responsibilities.

"A worker with a temporary visa has a legal stay in the United States," he said." And he obviously has all the rights, even the social rights, education, health care, so on. And from that point of view when he brings his family to the United States, he extends his rights to his family."

It was the reaction to these high social costs that helped former California Governor Pete Wilson in his campaign for a state law denying welfare, health and education benefits to illegal immigrants. In 1994, California voters overwhelmingly approved Proposition 187, but most of its provisions were later limited or blocked by the courts. Still, U.S. groups favoring tighter restrictions on immigration have cited California as a case where, in their view, an excess of immigrants caused a anti-immigrant backlash.

However, Mr Aguilar Zinser remains upbeat. He says the guest worker program together with President Fox's State visit to the United States, the first of any world leader during the Bush Administration, is certainly the dawn of a new era.

"What this is really reflecting is that times are changing, perceptions are changing, attitudes are changing, and this is a reversal of what happened some years back," he says. "All the skew years of Pete Wilson in California, when he ignited the anti-immigrant attitude. Today I think that the United States is willing to approach this from a much more mature perspective."

President Bush on many occasions has expressed his interest in having an agreement on the issue of migrant workers from Mexico. His interest in the immigration issue goes back several years. When he was governor of Texas, he publicly disagreed with fellow Republican Pete Wilson over the issue and made clear that there would be no Proposition 187 in his state.

Given the rapport he has with Mr. Bush, President Fox is hoping to return home with an initialed agreement, or at the very least a confirmed report of substantive progress for Mexican migrant workers.

However, Mr. Gonzalez says he does not believe that the whole guest worker deal will be ready to be initialed in time for President Fox's trip. Still, he says even a partial agreement will be of crucial political importance.

"Maybe a formal announcement that we are working on this issue and we expect we are going to conclude our negotiations in two, three or more [months], whatever. That will be an important achievement for President Fox," says Mr. Gonzalez.

This thorny issue has divided the United States and Mexico for many years and this latest development is being followed with great interest on both sides of the border.