Mexico vowed not to let the United States impose migration reforms on it as its leaders prepared Thursday to host US officials who are cracking down on undocumented immigrants.
Foreign Minister Luis Videgaray sharpened the tone as he prepared for talks following a diplomatic row over president Donald Trump's hard line on trade and immigration.
Trump has outraged Mexico by vowing to build a wall along the border to keep out migrants from Latin America, whom he branded rapists and criminals during his presidential campaign.
His government has issued new orders to begin arresting and deporting illegal immigrants, many of them Mexicans.
"The Mexican government and people do not have to accept measures that one government wants to impose unilaterally on another," Videgaray said late Wednesday.
"We are not going to accept that because we do not have to do it and it is not in Mexico's interests."
He said Mexico would use "all legally possible means" to defend Mexicans living abroad, including potentially appealing to the United Nations.
President Mexican Enrique Pena Nieto and Videgaray were scheduled to meet with US Secretary of State Rex Tillerson and Homeland Security chief John Kelly on Thursday.
US officials said the talks will focus on how to curb cross-border migration and drug-trafficking and to affirm their bilateral ties.
Trump's stance has strained previously good US-Mexican relations, said Maureen Meyer, an expert at the Washington Office on Latin America, a US human rights advocacy organization.
"Secretary Tillerson has an opportunity to set relations on a more sound footing based on mutual respect," she said in a statement.
Pena Nieto had canceled a planned meeting with Trump in Washington last month over the US leader's vow to make Mexico pay for the wall.
But White House spokesman Sean Spicer insisted Wednesday that Washington has "a very healthy and robust relationship with the Mexican government."
He said Thursday's talks aim "to improve the quality of lives for both people of Mexico and the United States by combating drug traffickers and finding ways to bolster both our economies through a broader relationship that promotes commerce and legal immigration."
US immigration authorities have arrested hundreds of people as part of Trump's pledge to crack down on undocumented immigrants.
Kelly on Tuesday issued new orders to step up the detentions.
Speaking in Guatemala on Wednesday before traveling to Mexico, Kelly said "to any citizen considering moving to the United States in crossing our boundaries irregularly — migration — my best advice is to not do it."
Mexico has hinted it could use border cooperation as a bargaining chip.
But in a move that may pressure Mexico, Trump has ordered US government agencies to count up how much aid they are giving to that country under different programs.
The United States has allocated $2.6 billion worth of aid to Mexico for fighting crime under the 2008 "Merida initiative," US officials say.
Mexico relies on the United States as a trading partner, sending 80 percent of its exports to its northern neighbor.
Vowing to protect US industry, Trump has called for a renegotiation of the North Atlantic Free Trade Agreement with Mexico and Canada.
Pena Nieto has promised to defend Mexico's interests and called for respect from the United States.
"Neither confrontation nor submission: the solution is dialogue and negotiation," he said last month.