Americans might expect that a relatively minor border incident between Colombia and Ecuador would not draw in the United States.

Unfortunately, the U.S. alliance under the Bush administration with the right-wing government of President Alvaro Uribe of Colombia and its ongoing scrap with socialist President Hugo Chavez of Venezuela has meant that even if Americans didn't want to be, they have been pulled into the three-cornered dispute involving Colombia, Ecuador and Venezuela.

It has caused the Organization of American States, in emergency session, to pass a resolution that said Colombia violated Ecuador's sovereignty. That leaves Colombia and the United States against the house -- a house including Brazil, South America's mega-country.

The incident began when Colombian troops drove five miles into Ecuador to attack anti-government forces of the Revolutionary Armed Forces of Colombia, killing two dozen last weekend. Ecuador was incensed by the attack and Mr. Chavez, moved by his friendship with its president, Rafael Correa, and his enmity for the United States, sided with Ecuador. Both Ecuador and Venezuela then moved troops up to their borders with Colombia.

Fortunately, Ecuador referred its complaint to the OAS, which is now laboring mightily to resolve the dispute.

The United States already has hundreds of its own forces in Colombia training and equipping its ally's troops. Washington also has provided Colombia some $5.5 billion in aid in recent years, third after only Israel and Egypt.

The U.S. troops in Colombia support the effort to prevent heroin and cocaine production and export to the United States, reinforce the Colombian armed forces' efforts against the FARC and help protect an oil pipeline there that belongs to the U.S. firm Occidental Petroleum. The United States quite legitimately does not want to see armed conflict between Colombia, Ecuador and Venezuela.

What is more difficult to see is what U.S. interests are served by its military presence in Colombia. The drug interdiction effort is considered to be a failure. The FARC is a problem the Uribe government should resolve for itself through negotiations. Finally, U.S. forces should not be deployed to protect a U.S. oil company's pipeline.

Why exactly is the United States in the middle of this affair?