SINGLE mother Felipe Perez is enjoying putting the squeeze on El Paso businessman Andre Diaz.After 16 years toiling in sweatshops here and across the border in Ciudad Juarez (where she lives), Ms. Perez figures it's time to balance the ledger. So three months ago, she became an organizer for the International Ladies Garment Workers Union (ILGWU). Decked out in her ILGWU T-shirt, Perez is walking the picket line with 120 garment workers, striking for unpaid wages and a union contract. This two-month-old strike is the first in El Paso in 20 years. It is significant, labor experts say, for two key reasons: First, this may be the last chance workers have before Mr. Diaz and the rest of the El Paso garment industry, spurred by a North American free-trade deal, jump to mostly nonunion Mexico. "We're fighting for a three-year contract to keep them from leaving," Ms. Perez says. Second, and perhaps more important, this clash has potential to spread union activism to Mexico's side of the Rio Grande. "If they win this strike, it will show people on both sides of the border it's possible to organize," says Kim Moody, at Labor Notes, a Detroit-based trade publication. David Young, an ILGWU campaign organizer, says the main newspaper in Juarez has followed the strike even more closely than El Paso newspapers. And he says, "We're getting feelers from a lot of independent unions on the other side of the border." The long-term goal of the union, Moody says, is not to unionize the Mexican garment industry, but to raise Mexicans' wages to levels that may preserve at least some garment-industry jobs in the US and Canada. Poor health and safety records at US-owned maquiladora factories in the mini-free-trade zone along the US-Mexico border, have been the recent focal point for US labor unions, environmentalists, and church groups campaigning against a free-trade agreement. But if conditions are so bad, why aren't Mexican unionists publicizing the problem and fighting for their members rights? "The Mexican labor unionists are not very effective because at the core they've got split personalities," says Edward Williams, a University of Arizona professor working on a maquiladora unionization study. "They are labor leaders, but they're also Mexican nationalists and politicians eager to cooperate with government programs designed to increase employment. Often they're too concerned with development and less concerned about social justice." It is something "that's not uncommon in developing countrie s." Also, except in the Matamoros area, which has a long tradition of union activism, unionism in the maquiladora industry is low. Of the 330 factories in Juarez, it is estmated that only 10 percent have unions. And, maquiladora workers are difficult to organize. "They're transient, women, and young," Prof. Williams says. But in some places along the border, the gap left by toothless unions or unionless maquiladoras is being filled. Because the maquiladora workforce is primarily women (although the margin is narrowing), grass-roots women's organizations have sprung up. And, US labor unions - discouraged by years of fruitless attempts to unite with Mexico's major trade unions - are starting to tap these women's groups. In organizing the El Paso strike, the ILGWU has piggybacked on the efforts of La Mujer Obrera, a 10-year-old women's group that organizes workers'-rights seminars, offers medical care, and a food cooperative. But perhaps the best example of a workers'-rights group is the Comite Fronteriza de Obreras (CFO). Active in six cities along the south-Texas border, some 10,000 women have belonged to the 11-year-old organization supported by US church groups. Small groups of maquiladora workers meet discreetly, usually in someone's home, to learn about their rights under Mexico's labor laws, translate warning labels on chemical containers that are often in English, and seek solutions to safety problems. "I learned I could defend myself," says Maria Guadalupe Torres Martinez, a CFO director in Matamoras. "It was a revelation that I had rights beyond the mere right to work." For 15 years Ms. Torres washed capacitors at Kemet, a subsidiary of Union Carbide, with her bare hands in a solution of methalyne chloride, a chemical linked by health authorities to cancer. When she learned, through CFO of the danger, she helped organize a successful campaign to correct this and other unsafe practices in the factory. That was five years ago. Today, she says, health issues are still the main concern. "Exhaust fans, which remove chemical fumes and dust, break down and don't get fixed," she says. Several of the women in CFO have gone on to form independent unions or lead in reforming existing unions. But five years ago, when the CFO went looking for support from US labor unions, nobody returned their calls. Suddenly, this year, the Amalgamated Clothing and Textile Workers Union invited CFO representatives to five district meetings. And the ACTWU is not alone. "We've been trying for 10 to 15 years to build a relationship with the Confederation of Mexican Workers [Mexico's largest union group]," says Victor Munoz, AFL-CIO regional representative in El Paso. "CTM officials say all the right things, but nothing happens locally. I think the right thing is to approach community organizations."Next: Congestion clogs US-Mexico border towns.