What's the 'economic rationale' for the Colombian PTA?

The Economist writes:

Nevertheless Mr Bush has repeatedly made the case for the Colombia trade deal not on its economic rationale, but because it would help a Latin American ally in the war on drugs, and incidentally one whose next-door neighbour is that anti-American irritant, Hugo Chavez, Venezuela’s president.

Um, what is the economic rationale for the US-Colombia PTA? It gives Colombia no new access to US markets, so it can’t be aid consumers. It may aid some US investors who want access to the Colombian telecoms market and US agricultural exporters will enjoy some gains. But it’s hard to get excited about the economic benefits of this trade deal, and it surely can’t be the best place for an unpopular administration to expend its little remaining political capital with respect to international trade.

I don’t find the security story a particularly compelling reason to support the agreement either. I spoke with Dan Fisk, Senior Director for Western Hemisphere Affairs, on Friday about potential for the PTA to improve Colombia’s security situation. Fisk described the economic benefits for Colombia largely in terms of making permanent the preferential market access Colombia currently enjoys. He said that investors are more likely to make significant long-term investments when trade preferences are permanent, rather than subject to legislative renewal as they are under the Andean Trade Preferences Act. He also argued that investors have been moving to Peru, which does have a PTA with the United States.

While these effects are plausible, I question their magnitude. In the end, this PTA is largely symbolic — for both international relations and domestic politics.