Writer Carlos Fuentes said Thursday the "blind and arbitrary" decision by the United States to build hundreds of miles of fencing along its Southwest border will be the biggest headache for President-elect Felipe Calderón.

In an article published Thursday in a Mexico City daily, Fuentes said Calderón, who will take office Dec. 1, "will have to fight with a double-edged sword" in his relations with the United States.

On the one hand, Calderón will have to keep in mind U.S. employment needs and its treatment of Mexican immigrants.

Conversely, on the domestic front, "as the border closes and heats up," the novelist, essayist and former diplomat said Mexico must find a way to "provide work to a half-million workers each year who are trapped behind a ´nopal´ curtain," referring to the number of Mexicans who migrate to the United States annually.

His reference to the nopal cactus was also an allusion to the Iron Curtain that separated Eastern and Western Europe before the fall of communism.

U.S. President George W. Bush has said he will sign a bill passed by the U.S. Congress last month authorizing the construction of a double fence along more than 1,126 kilometers (700 miles) of the U.S. border with Mexico. He also insisted on the need for comprehensive immigration reform that includes immigrant-friendly measures like a guest-worker program.

Fuentes predicted the immigration conflict will make Calder- ón´s term one of the more trying periods in relations with the United States in Mexico´s history.

Fuentes also said Calderón must establish better relations than his predecessor with a Congress that is "pluralist and combative, though I hope not dumb." According to the author, current President Vicente Fox, like Calderón of the conservative National Action Party, failed in this regard because he lacked an effective intermediary.

Good relations with lawmakers are essential to achieving "urgent (reforms) in the areas of public safety, hydraulic resources, electricity and oil, fiscal policy, and electoral politics: the re-election of lawmakers, presidential runoff," Fuentes said.