Donald Trump’s tough talk on Mexican immigration is generating a strong response from Mexico and highlighting some uncomfortable truths for both nations:

Long before it builds any new border wall, the United States will need Mexico’s continued cooperation to control immigration and the cross-border flow of drugs.

Likewise, Mexico needs the North American Free Trade Agreement (NAFTA) more than the US does. The more than $500 billion annual trade that flows between the two countries equals nearly half of Mexico’s yearly economic output or GDP; in the US, it represents only about 3 percent of GDP.

That offers some basis for negotiation between the two neighbors. Mexican President Enrique Peña Nieto has said that Mexico is open to negotiations, but that his country will do everything it can to protect NAFTA.

“Mexico should use its national security apparatus as a counterweight to economic negotiations,” says Alejandro Hope, an independent security expert based in Mexico City.

For the moment, relations are as strained as they’ve been in decades.

Last August, largely ignoring Mr. Trump’s harsh Mexico campaign rhetoric, President Peña Nieto rolled out the red carpet for him when he visited Mexico. But any hopes that the president-elect's pronouncements were mere campaign bombast were dashed at his press conference last week. He restated plans to build a wall separating the two countries, a wall he said Mexico would pay for, and to introduce tariffs on products made south of the border.

Mexico’s reaction was uncharacteristically swift. Peña Nieto told diplomats last week that all facets of the prized bilateral relationship were now up for discussion, including Mexico’s efforts to stem immigration and cooperate on security matters.

“What Peña Nieto should say is, ‘These are our red lines. If you want to build a wall, then you will be responsible for stopping everything that comes from Mexico: drugs, migrants, and terrorists,’ ” says Jorge Castañeda, a former Mexican foreign minister.

Illegal immigration near 40-year lows

The push for a wall comes at an unusual time. The number of undocumented migrants apprehended at the US/Mexico border – a rough proxy for the flow of illegal immigrants – is at or near its lowest level since the 1970s. And Mexicans accounted for fewer than 1 percent of apprehensions last year, according to the Washington Office on Latin America, a research and advocacy group based in Washington, D.C.

The number of Central American apprehensions, however, has been rising – as more than 80,000 women and unaccompanied minors in 2016 were apprehended on the US border. This surge in Central American migrants and the accompanying pressure from the Obama administration led Mexico to launch the Southern Border Program in July 2014. The effort includes detentions, stricter border control, and deportations aimed at securing Mexico’s southern border.

Last year, Mexican authorities deported more than 150,000 Central American migrants traveling to the United States and detained more than 425,000 migrants between 2014 and July 2016, substantially easing the financial and administrative burden on United States border authorities.

Those efforts give Mexico leverage in any upcoming negotiations. “You can do a friend’s dirty work, but you don’t do an enemy’s dirty work,” Mr. Castañeda points out.

Mexico could even make it more difficult for the United States to control its border. Purported Mexican citizens are currently deported back to Mexico even though many carry no official identification papers in an effort to avoid detection. Castañeda suggests that Mexico could also fund contested deportation hearings in the United States, thereby saturating the immigration system.

Timing also works in Mexico’s favor. Even if Trump goes ahead with a proposed $11 billion wall, the project will take years to complete.

“Mexico’s continued collaboration on stemming the flows of Central American migrants is an issue of enormous importance and Mexico will continue to play that card in the negotiations ahead,” says Duncan Wood, director of the Mexico Institute at the Wilson Center, a policy forum based in Washington.

Terrorism and drug help, too

Mexico and the United States also cooperate extensively in tracking potential terrorists, reducing the flow of drugs into the US, and capturing drug traffickers. A year ago, Mexico captured Joaquín “El Chapo” Guzmán, head of the Sinaloa cartel, the most active criminal organization smuggling illegal drugs into the US. Mr. Guzmán was extradited to the US Thursday to face drug trafficking and oher charges after losing a legal battle in Mexico.

However, Mexico could become far less helpful in the face of a hostile United States government, says Mr. Hope.

Mexico eradicated 21,425 hectares (nearly 53,000 acres) of opium poppy in 2014, the latest figures available. It also seized 19.8 metric tons of methamphetamine and 3.6 metric tons of cocaine. If Mexico were to stop cooperating in supply reduction, Hope predicts an enormous increase in heroin flow to the United States.

US efforts to take down major drug kingpins would likewise be more difficult if Drug Enforcement Agency operatives were shut out from joint operations.

Whether Mexico can leverage its security and migration efforts for a solid economic deal remains unclear. Trump's pressure on the car industry, a key Mexican growth sector, likely played a role in car manufacturer Ford canceling its $1.6 billion investment in a factory in central Mexico. The president-elect’s rhetoric has also sparked fears that other carmakers such as GM may follow suit.

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Those fears, together with the uncertainty about what a US tariff on Mexican imports might look like, have driven the peso to historic lows this year, forcing Mexico’s central bank to intervene.

“Mexico will be forced to give something in exchange for keeping NAFTA, because Trump needs to be able to go back to the American people and say, ‘I got this, I negotiated and I won,’ ” concludes Wood.