Flights from the base at Manta, where a Navy P-3 surveillance plane prepared to take off, have become an important element in the drug war.

"It's an advance post for combatting narco-trafficking," he said firmly in an interview, and as such very welcome. "We don't feel we are being invaded by the Americans here. It's as if someone has come along and offered to build us a second story on our house for free, so of course we are going to say `go right ahead.' "

However you describe it, the flights that leave here daily have already become an important element in the United States' efforts to halt drug trafficking.

With the conflict in neighboring Colombia worsening and the American commitment there growing, a new foothold so close to the theater of action will "improve our response time and enhance our ability to detect and monitor flows of cocaine and heroin," Gen. Barry R. McCaffrey, the White House drug czar, said in an interview earlier this year.

The work here, which includes construction of living quarters for 200 American military and civilian contract personnel, is scheduled for completion late in 2001. Then the "forward operating location," as it is called, will be able to provide round- the-clock tracking of activity in Colombia and neighboring countries through a pair of Awacs surveillance planes, among America's most sophisticated, and tankers to refuel them in the air.

The major coca-growing areas of Putumayo and Caquetá are just a few minutes' flight time north of here, but the planes will also be able to monitor air and marine activity well into the Caribbean.

Until last year, such missions were flown out of Howard Air Force Base in Panama. But when the United States and Panama failed to agree on use of the base after the United States handed over the Panama Canal a year ago, the Pentagon and State Department were forced to shop for alternatives.

Two smaller outposts in the Dutch colonies of Aruba and Curaçao in the Caribbean were quickly found, and Jamil Mahuad, then Ecuador's president, agreed to a 10-year deal in November 1999 calling for an upgrading of the existing Ecuadorean Air Force base here. But two months later he was overthrown in a military coup, and complaints and challenges to the base are yet to be resolved.

Officially, the American presence here is merely a counternarcotics observation post and has nothing to do with Colombia's war against leftist guerrillas or with Plan Colombia, the $1.3 billion American aid plan for Colombia. But since the guerrillas earn money and arms from drug trafficking, that distinction seems increasingly unconvincing to Ecuadoreans worried about getting dragged into the conflict.

"This base is a provocation to all of the irregular forces in Colombia," Antonio Posso, an influential leftist member of Congress, said in an interview in Quito, the capital. "Our oil pipeline has already been attacked by Colombian guerrillas, and the paramilitary groups are killing people on Ecuadorean territory, so just imagine how a military installation like this acts as an enticement."

But the "agreement for cooperation" between the United States and Ecuador specifically states that the base here shall be used "for the sole and exclusive purpose of supporting aerial detection, monitoring, tracking and control of illegal narcotics trafficking." And Mr. Zambrano and other Ecuadorean supporters of the project argue that since trouble is likely to be coming anyway, it is in their country's interest to be prepared and have some American protection.

"The nature of the conflict in Colombia and the way it is moving southward are such that they are going to provoke a spillover whether the American detachment is here or not," said Col. José Bohorquez, the Ecuadorean commander of the air base here. "It is the result of geography and the situation in Colombia, not of the American presence, and we should be clear about that."

Though the United States is paying the entire cost of expanding the existing base and will rely to a large extent on the local economy for labor, supplies and equipment, the agreement does not require Washington to pay rent or local taxes during the period of the agreement. But this is a country burdened with $13 billion in foreign debt and a poverty rate that has doubled in the past three years, and many people had hoped for more generous terms.

As a result, the popular perception in many parts of Ecuador is that the base "was given away in exchange for nothing during a moment of economic pressure," said Adrián Bonilla, a researcher for the Latin American Faculty for Social Sciences in Quito. "Mahuad assumed that the United States would help him get an accord on the foreign debt as a sort of payback, and agreed to give Manta away without a real process of negotiation."

Since the document the two governments signed is an agreement and not a treaty, the government was able to press ahead on the project without a vote in Congress. But a challenge to the legality of the accord has been taken to Ecuador's highest court, and Ecuador's Congress is also clamoring for a look.

"This agreement needs to be reviewed, and it will be reviewed," Mr. Posso vowed. "Until Congress has approved this measure, it is simply not valid, and approval will depend on whether or not Congress judges the conditions to be beneficial to the Ecuadorean nation. We are all against narcotics trafficking, but if this gets us involved in the war against the Colombian guerrillas, then things get complicated for us."

Opposition to the base seems especially pronounced in Guayaquil, the country's largest city and commercial center, but for reasons that appear to have more to do with business than politics. Guayaquil has long enjoyed a monopoly on air shipments of bananas, flowers and fish, which a second Pacific Coast international airport here would surely challenge.

Trying to be sensitive to Ecuadorean concerns about sovereignty, American military officials have adopted a policy of what they call "minimizing our footprint." When they are off base they dress in civilian clothes, and they have eagerly plunged into community life here with programs to train firefighters, paint schools and churches and coach basketball teams.

A group calling itself the Marxist- Leninist Communist Party of Ecuador has posted graffiti demanding that "warmongering Yankees get out of Manta." But for the most part, residents here, from shoeshine boys up to the business elite, seem to welcome the American presence, or at least the dollars that have begun to be injected into the local economy.

"With the Americans here, I am certain that many new jobs are going to be created and lots of money will be spent," predicted Margarita Macías Farfán , a shop clerk. "We already see them in the restaurants and hotels, and we hope that many more of them will come and invest here so that our lives improve."