The idea was to restore the rule of law, to bring order to a chaotic situation. The results became more and more apparent. Crime rates went down in the border region. Today, the number of migrants crossing is at a 30-year low. That's because of years of bipartisan work on this issue.

The work the Mexicans are doing in terms of migration control on Mexico's southern border is crucial to our own border security.

Not only are the numbers of migrants entering the United States at the lowest levels in a generation, but they are now largely Central American. Four out of five border-crossers detained in South Texas are Guatemalan, Honduran or Salvadoran. They are driven by violence and poverty in their home countries and the desire for family reunification.

To the extent that President Trump means strengthened border security, I am fully in favor of the idea that the rule of the law, secure borders and public safety should prevail. Drugs should not enter illegally. Migration should take place in accordance with lawful norms and secure and safe procedures.

We should be wary, particularly with our closest friends and allies, of breaking down the trust and confidence that lie at the foundation of relationships.

In the course of 25 years, we have developed a constructive relationship with Mexico that was nonexistent before. During the last eight to 10 years there have been continued efforts which have resulted in a strategic alliance with the Mexicans and improved safety and security at the border.

Most people who live at the border or are familiar with the border know that a Berlin-like wall stretching from San Diego to Brownsville is not necessary. And the costs would be prohibitive. And there are places on the border, such as the Arizona desert or the open terrain around the Big Bend in South Texas, where Mother Nature has created her own barrier that is not easily passable. Or if you do pass through it, you are easily detected.