Trump plans to visit the Mexico border in California on Friday, where some aides are bracing for a possible announcement. Even though White House officials had begun deliberating, business groups expressed skepticism that any plan might work in a way that limits potential problems.

As Trump has escalated his threats to close the border in recent days, top aides have launched a two-pronged strategy in preparation for a decision.

One approach has been to study ways to minimize the economic impact of shutting the border with the United States’ second-largest trading partner, in part by allowing trains and trucks to continue bringing goods across the border.

The second prong has included internal warnings to Trump about what might happen if the border is sealed, messages delivered by National Economic Council Director Larry Kudlow and Kevin Hassett, head of Trump’s Council of Economic Advisers.