It's been almost a year since the U.S. government agreed to invest more than $1.3 billion in a wide-ranging anti-narcotics program known as Plan Colombia. The program aims to eliminate half of Colombia's cocaine production over five years. But its aerial spraying to knock out drug crops has been controversial. This week, Colombia received its first high-level U.S. government delegation under the new Bush administration.

U.S. Undersecretary of State Marc Grossman, who led the delegation on its three-day visit, gave an assessment of the anti-drug strategy at a news conference Friday. "The combination of aerial spraying and voluntary manual eradication by farmers who made pacts with the government has had a serious impact on drug production in southern Colombia," he said. "50,000 hectares of coca plantation have been sprayed from the air nationwide in what we believe is a safe and environmentally sound manner."

To destroy the crops, the aerial fumigation program uses the chemical glyphosate, commercially known as Round Up. That's become controversial in recent months, as residents in the drug growing zones complain the spraying is causing skin and eye infections. Mr. Grossman says the U.S. administration has looked into the issue. "If you are in contact with the glyphosate in high enough concentrations, it does cause eye irritations, but the way we spray it, and the levels with which we spray it, are so low, that we don't believe this is a problem in the short term or the long term," he said.

The visit comes at a time when peace talks with the country's largest left-wing guerrilla group, the FARC, are teetering precariously. There is mounting criticism that the rebels are making unfair use of a huge demilitarized zone, created to allow for peace negotiations, as their own private refuge to hold kidnap victims, process narcotics and train troops. Some critics have called for the zone to be eliminated, which would likely mean an end to peace talks. Mr. Grossman did not agree. "The establishment and continuation of such a zone is purely and wholly and solely a matter for the Colombian government," he said. "I made no recommendations to President Pastrana. What I did was agreed with President Pastrana that there is a need to restart the peace process."

In mid-September U.S. Secretary of State Colin Powell will visit Colombia and Peru, as part of the continuing evaluation of the U.S.-backed anti-drug strategy.