KABUL, Afghanistan -- A recent move by the United States military to bar one of Afghanistan's major airlines from contracts because of allegations of narcotics smuggling has caused a diplomatic firestorm, with Afghan officials angrily demanding proof and some American officials quietly criticizing the timing of the decision.
The blacklisting of the airline, Kam Air, is said to have started early this month and was first reported by The Wall Street Journal on Friday. The article quoted American military officials as saying the ban on American military contracts was based on information that the airline had carried "bulk quantities" of opium out of the country as well as within it.
Kam Air officials deny the accusation, and the Afghan government says it has no knowledge of such activities. President Hamid Karzai's spokesman, Aimal Faizi, demanded that the American military hand over any evidence it had so that the government could act on the charges.
"We have to get to the bottom of this in order to take action," Mr. Faizi said. "We need evidence and proofs in this regard. We cannot make inquiries based on a newspaper article."
Several Western officials here, speaking on the condition of anonymity because the issue is a delicate one, described the Afghan demands as reasonable, given the potential complications. The American military command and the American Embassy declined to comment on the accusations and Afghan response.
One part of the dispute is a practical problem: Mr. Karzai often charters Kam Air for foreign trips, and planned to do so in the next few days for a flight to Europe, Mr. Faizi said. If the airline has been publicly listed for drug smuggling, Western officials noted, other countries' air traffic controllers and aviation regulators will not want Kam Air planes landing on their runways.
"This is being taken very seriously by air control and aviation authorities around the world," said one Western diplomat here. "We don't know what kind of evidence there is, but the allegations have damaged the reputation of the company so much they may not be able to fly."
The Kabul government is also worried because the accusation implicitly calls into question airport security and customs procedures in Afghanistan. A formal note sent to the American Embassy from the Afghan Foreign Ministry this week demanded "all documents" related to the allegations.
"These accusations are very serious," the note said, "and not only damage the credibility of Kam Air airways, but also raise doubt about the work and inspections of related organs of the Islamic Republic of Afghanistan."
Potentially more serious, the allegations have inflamed longstanding tensions between the American administration and Mr. Karzai about American charges that his government is corrupt.
Some American officials privately expressed dismay at the military's decision, saying it blindsided and embarrassed Mr. Karzai just after his successful meeting in Washington with President Obama and during negotiations over the long-term relationship between the countries.
Both American diplomats and the military have been ambivalent about how to approach Afghan corruption cases over the years. While they have at times pushed for more official accountability as in the Kabul Bank corruption scandal, in which some members of Mr. Karzai's family and inner circle have been implicated, in other areas they have backed off. Often, American officials say, that softer approach has come in the hope that Americans will ultimately have more influence if they avoid nettling Mr. Karzai -- though that view has been hotly debated.
"There's a family dispute going on," one Western official said, speaking of a difference between American military and diplomatic officials over the Kam Air decision. "People are spun up. This could have far-reaching effects."
As in many corruption cases, the allegations of drug smuggling are based on intelligence, making it less likely that the United States military will share the information and leaving leeway for the Afghan government to deny them.
The head of the airline, Zemarai Kamgar, has denied the accusations repeatedly on Afghan television, and other Afghan businesses have rallied behind him.
"Such reports have a bad effect on current businesses in Afghanistan, and we are suffering a lot," said Hajji Yunnis Mohammed, a deputy head of the Afghanistan Chamber of Commerce.
"Our businessmen are concerned about 2014," Mr. Mohammed said, referring to the completion of the American troop withdrawal, "and when there are drug smuggling allegations and threats of being blacklisted, that damages business prospects in our country."
Mr. Faizi, the presidential spokesman, added: "We get reports from time to time about foreign aircraft smuggling drugs, but this is the first time we have heard anything about Kam Air."
When it comes to drug smuggling, Afghanistan has a troubled record. It is the world's largest opium producer, and traffickers smuggle hundreds of tons of opium out of the country every year on routes to Iran, Tajikistan and Pakistan. Although some of it may go by air, much of it crosses by land, carried by trucks, private vehicles and burros.
Hundreds of millions of dollars in cash also leaves the country every year, smuggled through the airports in suitcases. And gold has recently emerged as a favorite export -- although that is taken out legally.
Sharifullah Sahak contributed reporting.
This article originally appeared in The New York Times.