For the second time in a month, the United States on Wednesday demanded Mexico look into a case of a company in the auto industry blocking worker efforts to unionize.

US President Joe Biden ran for office as a champion of American workers, and pledged to take action to ensure they are protected from unfair competition from cheap labor in other countries.

The US Labor Department and the US Trade Representative formally called on the Mexican government to review whether workers at the Tridonex auto parts facility in Matamoros were denied rights of collective bargaining guaranteed under the continental free trade pact.

Last month, Washington filed its first formal complaint under the United States-Mexico-Canada Agreement (USMCA) over allegations of "serious violations" of worker rights during a recent union vote at a GM plant in Silao, in the state of Guanajuato.

The latest action is in response to a formal complaint lodged against Tridonex, a subsidiary of Philadelphia-based Cardone Industries Inc, by labor organizations including the US labor federation AFL-CIO and Mexico's SNITIS industrial workers union.

The complaint said workers were "harassed and fired for trying to organize with SNITIS, an independent Mexican union," rather than the management-backed union, and labor lawyer Susana Prieto Terrazas was imprisoned by local authorities.

US Labor Secretary Marty Walsh said the government will enforce provisions of the USMCA trade pact to ensure Mexican workers are able to unionize
US Labor Secretary Marty Walsh said the government will enforce provisions of the USMCA trade pact to ensure Mexican workers are able to unionize AFP / MANDEL NGAN

"Workers' ability to exercise their fundamental human rights to freedom of association and collective bargaining without retaliation is essential to building independent unions in Mexico," US Labor Secretary Marty Walsh said.

"Using the labor enforcement mechanisms in USMCA is a critical step in assuring that US and Mexican workers share in the benefits of trade."

Under the USMCA, Mexico has 10 days to conduct a review to determine if a violation took place and 45 days to attempt to address it.

The Mexican government late Wednesday acknowledged receiving the request, and said it will review it to "determine with facts and legal elements whether or not there is a denial of labor rights based on the commitments assumed" in the USMCA.

If so, a joint statement from the ministries of Economy and Labor said they will seek to reach "a path of reparations" with its US counterparts.

If the two sides cannot agree the issue has been resolved, the United States may request that a panel make a determination.