U.S. Secretary of State Rex W. Tillerson  and Homeland Security Secretary John F. Kelly visited Mexico this week, calling the visit “a step toward mutual understanding”  as they sought to cool off tensions that threaten to derail trade and other key agreements between Mexico and the United States.

However, it appears the relationship between the two nations continues to fray.  President Trump has issued a new immigration order to round up and deport immigrants who are in the United States illegally and directing U.S. authorities to deport to Mexico all those who crossed the southern border illegally, even if they are not Mexican nationals. Non-Mexicans sent back to Mexico will have to await the outcome of their deportation proceedings there.

Also, the Trump administration is requiring government officials to review and calculate all the money and grants that the United States provides to Mexico.  That calculation is due today and it seems to suggest that there is a link between the constructionof the border wall and the foreign aid and support that the United States provides Mexico.

In addition, last month there were heated words between President Trump and Mexico’s President Enrique Pena Nieto, over who should pay for a wall on the southern U.S. border. The Trump administration implied that a 20-percent tax on goods from Mexico would be one way to pay for the wall.  The disagreement and concerns about a trade war led President Pena Nieto to cancel his planned visit with Trump in Washington.

White House officials said that yesterday’s day-long meeting covered an ambitious agenda including border trade, strengthening Mexico’s southern border with Central America and collaborating on combating drug trafficking and terrorist threats emanating from Mexico.  Energy security and Mexican economic policies, as well as 1.5 billion in daily commerce,  were also discussed.

However, Mexico officials drew a sharp line against “unilateral” U.S. immigration policies before the talks even began.  Mexican Foreign Minister Luis Videgaray said this week that the Pena Nieto government plans to fight Trump’s immigration order. “I want to say clearly and emphatically that the government of Mexico and the Mexican people do not have to accept provisions that one government unilaterally wants to impose on the other,” Videgaray told reporters in Mexico City.  “We will not accept it because there is no reason why we should and because it is not in the interests of Mexico.”

If relations between the United States and Mexico worsen significantly, Mexico could limit or stop Mexican cooperation on a range of fronts, analysts say.  Beyond the billions of dollars in trade, the two countries cooperate on many security issues.  Mexico could limit its sharing of information, like the lists of passengers aboard international flights, and loosen visa rules for citizens of nations suspected of harboring terrorists.

Mexico could also detain fewer unauthorized migrants traveling from Central America and thus allowing more people to reach American borders.  Mexico, which has long provided a militarized buffer against the flow of drugs to the United States, could also relax its prosecution of the drug war.