U.S. Secretary of State Colin Powell and Foreign Minister Luis Ernesto Derbez will lead their teams at the conference. However, both sides have been very anxious not to raise expectations too far; there was heavy publicity for previous talks on the issue in 2001 but they foundered soon after the terrorist attacks of Sept. 11.

"We want to advance the subject of migration in all these paths," President Vicente Fox told journalists last week. "Finally, the proposal is to have an integrated agreement. But we must not create expectations too far ahead of reality. We've had months with no advances." Roger Noriega, U.S. assistant secretary of state for western hemisphere affairs, was also cautious, saying the United States was continuing to look for ways to make progress on the issue. But he added: "As you all know, of course, our immigration laws are made by Congress; there's been some activity in our Congress that has gained a lot of interest. But I want to take particular care not to raise expectations."

Immigration is a core concern in the relationship between the United States and Mexico, but Noriega indicated that progress was more likely on lesser priorities such as sending Peace Corps volunteers to Mexico for the first time and establishing a homeland-security hot line between the two countries.

The meetings, scheduled for Wednesday, are an annual event and are expected to involve 17 Cabinet secretaries from both countries, as well as dozens of lower-ranking officials. This year's gathering comes after a reconciliation between President Bush and Mexican President Vicente Fox, whose close relationship had cooled after Mexico refused to support the war in Iraq.

Mexican officials have said they are coming to Washington in search of agreement on a timetable for getting immigration reform moving again.

A major immigration-reform bill is pending in Congress. Republicans from the Arizona congressional delegation, including Sen. John McCain, proposed a formal "guest worker" program earlier this year to legalize migrant laborers. With about 20 million Americans of Mexican ancestry, the Hispanic vote could be important in next year's elections.

The issue is of vital importance in Mexico as it is believed that more than 4 million undocumented Mexicans work in the United States. Remittances from migrant laborers are expected to exceed US12 billion for the year, making it possibly Mexico's biggest source of foreign funds after oil exports.

Fox invested much political capital in his 2001 negotiations with U.S. President George W. Bush, while Jorge Castañeda, his first foreign secretary, spoke of aiming for the "whole enchilada" a comprehensive accord.

The new approach, according to Derbez who took over foreign affairs when Castañeda resigned in January is to take the enchilada "slice by slice."

Rather than concentrate all its efforts on the federal government, Mexico is taking a threepronged approach, which also includes talks with congressional leaders and local politicians in the most affected border states.

The McCain guest-worker proposal would provide visas for Mexicans to work in specific jobs, with agriculture probably the most important sector.

A guest-worker program specifically for agriculture might be the least controversial option. In many ways, such a scheme would merely reflect reality, as many swathes of the U.S. agricultural industry are already reliant on migrant labor.

However, some U.S. officials fear such a program, if not accompanied by other more significant concessions, might seem to Mexicans to be confirming their status as nothing more than low-wage laborers.

As for other issues on the table, Peace Corps spokeswoman Barbara Daly said representatives of the two countries have been talking for months about a program that would send volunteers with technical backgrounds to Mexico. Mexico has declined development assistance in the past.