Mexico, supported by 27 other nations, made a declaration at the Organization of American States slamming U.S. plans to build hundreds of miles (kilometers) of fence on its southern border.
The declaration, read aloud Wednesday at the OAS headquarters in Washington, said the barriers would not solve the immigration problem and urged the U.S. government to rethink its position, according to press releases from the OAS and Mexican foreign ministry.
The 28 nations express "deep concern regarding the decision adopted by the United States of America to build and extend a wall on its border with Mexico, considering it to be a unilateral measure that goes against the spirit of understanding," it said in the declaration, which was read out by Mexico's Ambassador Alejandro Garcia Moreno.
The United States refused to sign the declaration, with its Ambassador Robert Manzanares saying it could not attack a decision made by its legislative bodies, according to the OAS release.
Last month, the U.S. Senate approved a bill to build 1,100 kilometers (700 miles) of border fencing. U.S. President George W. Bush has said he will sign it into law, despite pleas from the Mexican government for a veto.
Mexican President Vicente Fox has called the plan "shameful" and compared it to the Berlin Wall.
An estimated 11 million Mexicans live in the United States, about half them illegally.
The 27 nations that supported Mexico in Wednesday's declaration were Antigua, Argentina, Barbados, Belize, Bolivia, Brazil, Colombia, Costa Rica, Chile, Ecuador, El Salvador, Granada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Nicaragua, Panama, Paraguay, Peru, San Kitts and Nevis, San Lucia, San Vicente, Suriname, Uruguay and Venezuela.
Mexico has also said it will challenge the fence plans at the United Nations.