Felipe Calderon, the Mexican president, has criticised a new immigration law in the US state of Arizona which permits authorities to question and detain suspected illegal immigrants even if they are not believed to have committed a crime.
Calderon said on Monday in Mexico City that the anti-illegal immigration law, signed last Friday, would cause hate and discrimination.
"A legislation, which opens the doors to unacceptable racial discrimination, is set in motion," Calderon said at a meeting with immigrant groups.
"Mexico's government will use everything in its power to defend the rights of Mexicans who are affected by this legislation and we'll spare no effort to ensure the dignity of every fellow compatriot.
Laura Carlsen, director of Americas Policy Program, spoke to Al Jazeera from Mexico City:
"Calderon has said he will not take this sitting down and has vowed to send legions of lawyers to fight this law, and defend individual cases of Mexicans in Arizona who have been subject to this law."
She said that since the US does not participate in many of the international legal instruments, like the UN convention on the rights of migrant workers, Mexico has very little legal leverage to challenge the law directly.
But much of Arizona's wealth and success is believed to be built on the backs of Mexican immigrants.
"It would be difficult to understand the growth and prosperity of the United States in the 20th century without the help and contribution of Hispanic and Mexican workers," Calderon said.
"It would also be very difficult to expect a solid economic recovery in the United States if the work of migrants is excluded in any way, because it's highly lucrative."
Carlsen said that under Nafta, the North American Trade Agreement, there is no clause allowing for even major violations of human rights
"What happened is that with US imports into Mexico [under Nafta], an estimated 2 million Mexican farmers were displaced and no longer able to make a living off producing farm products.
"Now Arizona uses a massive amount of Mexican farm workers to harvest its crops.
Calderon is to meet Barack Obama, the US president, next month in Washington DC, when he will bring up the issue, he said.
The tough new law in Arizona, that borders Mexico, requires legal immigrants to carry documentation at all times. It is slated to be introduced 90 days after the current legislative session adjourns.
It has heightened fears that Hispanic immigrants will be racially profiled.
"What is a father to do if, in 90 days, they can be stopped by any police officer and questioned ... when their family is at home and their kids in school?" Elias Bermudez, the founder of Phoenix nonprofit Immigrants Without Borders, said.
"That's going to create havoc, so a lot of them are saying, 'Look, before they pick me up, I'd rather leave the state of Arizona either to another state or back home'."
Jan Brewer, Arizona's governor, who signed the bill into law, has said that the costs of uncontrolled immigration and poor enforcement by the federal government has caused the state to act independently.
Given the long border between Arizona and Mexico, the state has a history of tough laws that have been unsuccessful in deterring undocumented immigrants from making the short, but often perilous, journey across the desert border region.
Obama criticised the law last week, stating that it was "misguided", and protests against it have been held outside the Arizona state capital building, which has also been vandalised.
More demonstrations are planned for the coming weeks against what will be the harshest anti-illegal immigration law in the US.
The law makes it illegal to hire day labourers off the street and to transport illegal immigrants.
It also requires state and local police to decide whether people are in the country illegally should they have "reasonable suspicion".
There is also concern in Arizona that the new law could have an impact on tourism to the state, and Mexican leaders have previously said that it may affect bilateral ties and trade.
The 3,200km US-Mexico border is said to be the busiest in the world. A total of about $1bn-worth of goods passes over the frontier in either direction every day and about 350 million people cross it annually.
It is believed that there are about 10.8 million people living illegally in the US, with an estimated 460,000 in Arizona.
The law is backed by Republicans in the state legislature and looks set to cause a standoff in November congressional elections in which the Democrats will be defending majorities in the senate and House of Representatives.