U.S. policy toward Colombia, America's third-largest aid beneficiary, has turned into a sinkhole of money and military resources over the past five years.

The stated rationale for the heavy U.S. involvement in Colombia is the proposition that drug use in the United States can be reduced by suppression of production overseas. Colombia was the prime case in point for this approach.

But it hasn't worked. Over five years a U.S.-financed air force, including helicopter gunships, has defoliated an estimated 1.3 million acres of coca plant and opium poppy fields in Colombia. In spite of this effort, the 90 percent of the cocaine and 50 percent of the heroin on U.S. streets attributed to Colombian traffickers has not been reduced at all; it may even have increased.

The price tag for "Plan Colombia," conceived in the Clinton years and carried out for the past four under the Bush administration, is nearly $3 billion, putting Colombia after only Israel and Egypt among America's largest aid recipients. The plan also included training of the Colombian military, which has also helped them substantially in fighting insurgents opposed to the government of conservative president Alvaro Uribe.

Instead of pulling the plug on this unsuccessful enterprise, the Bush administration is now asking for $734 million more to finance it for yet another year.

It is worth asking why. One reason might be that the 800 U.S. troops and contractors now in Colombia, doubled last year, are training and supporting Colombian military forces. Those forces are, in addition to carrying out the defoliation program, also guarding an oil pipeline owned by Occidental Petroleum, near and dear to Bush administration oil industry associates.

Another reason might be that the principal defoliant in use in Colombia, glyphosate, sold commercially as Roundup, is provided under a profitable contract by Monsanto. That company gave $3 million in contributions to Republicans in 2004, 75 percent of the company's overall campaign financing.

A third reason might be a desire on the part of the Bush administration to support Colombia's president Alvaro Uribe, a conservative swimming against a growing tide of left-leaning presidents elected in Latin America. Mr. Uribe is seeking to amend the Colombian constitution to permit himself a second term in office.

There is also talk in Latin America that the Bush administration wishes to retain its military relationship with Colombia in order to provide a base for a possible invasion of neighboring Venezuela. That country's president, Hugo Chavez, is the administration's current favorite enemy in Latin America, second only to Fidel Castro of Cuba.

None of these reasons sound good enough to justify continuing to spend billions of American taxpayers' dollars in Colombia, against the clear evidence that Plan Colombia has failed miserably in its impact on cocaine and heroin availability in the United States.

The Congress should scrap Plan Colombia now, rather than throw more good money after bad. It is easy to think of better uses for $3 billion.