Mexico has opened legal aid centres at consulates in 50 US cities, in a move designed to protect its citizens from tougher immigration enforcement.
Mexican Foreign Minister Luis Videgaray reaffirmed concerns about the human rights of Mexicans in the US.
But migrant defence centres would not "promote illegality," he said.
Mexico is worried about the impact that guidelines issued last month by President Donald Trump will have on the lives of its citizens.
Mr Trump ordered federal agents to join local police and immigration officers to enforce deportation procedures.
Millions of Mexicans who have lived in the US for many years are suddenly facing the prospect of fighting a lengthy and costly legal battle against deportation.
The new defence centres will provide free legal assistance for Mexican citizens who feel that their rights in the US are being threatened.
'Concern and irritation'
Bilateral relations have reached its lowest point in decades.
A week after being sworn in January, Mr Trump reaffirmed his intention to build a wall along his country's southern border, which extends for 3,200km (2,000 miles).
He insisted that Mexico would have to bear the cost of the proposed wall.
The remarks prompted President Enrique Pena Nieto to cancel a visit to Washington on 31 January and to announce extra funding to protect the rights of Mexican citizens in the US.
During a visit to Mexico by last month by US Secretary of State Rex Tillerson and Homeland Security Chief John Kelly, Mr Videgaray said President Trump's policies towards Mexico were a source of "concern and irritation".
There are an estimated 11 million illegal immigrants in the US. Six million of them are reportedly Mexican citizens.