President Bush, left center, and first lady Laura Bush, right center, meet with local growers Sunday during a tour of Alternative Development Products at the Casa de Narino in Bogota, Colombia.

Bogota, Colombia ? Amid tight security, the presidents of the United States and Colombia vowed an ongoing alliance to fight the drug trade and the rebel groups that feed off it.

“This country has come through some very difficult times,” President Bush said at the side of President Alvaro Uribe, a close ally whose country receives more U.S. aid than any outside the Middle East. “I’m looking forward very much to … continuing to work with you to defeat the drug lords and narco-traffickers – the narco-terrorists.”

Bush has proposed about $700 million in direct annual aid on top of the $4 billion Colombia has received since Uribe took office in 2002. He prodded Bush for even more, saying U.S. support has helped curb crime, corruption and the drug trade and weakened left-wing guerrillas and right-wing paramilitaries.

But a scandal linking top Colombian officials to brutal right-wing groups blamed for countless massacres in a 42-year civil war cast a shadow over the visit. Eight Uribe allies in Congress have been arrested. The foreign minister resigned when her brother and father were implicated. Bush asked Uribe about the scandal, and said he came away assured.

“If there are members of this government that have any links to these organizations, they will be immediately removed from their offices,” Uribe said. “Our commitment is the full defeat of terrorists and the total recovery of justice and of democratic institutions.”

Bush spent six hours in Bogota, all inside two of the city’s most fortified buildings, the presidential palace called Casa de Narina, where he received a red-carpet welcome with military honors, and the U.S. embassy.

About 2,000 protesters gathered about a mile from the palace chanting “Down with Bush” and burning American flags. Scattered graffiti called him an assassin.

Security was extraordinarily tight. One unusual tactic involved an entire decoy motorcade. More than 20,000 police and security personnel were deployed.

A key focus of Sunday’s meeting was a six-year-old joint project known as Plan Colombia, which aims to quell violence and drugs. Spraying has wiped out record acreage of coca. But street prices remain near all-time lows.

“We’ve spent a tremendous amount of money, and the amount of stuff is the same as ever,” said Riordan Roett, director of Latin American Studies at the Johns Hopkins School of Advanced International Studies. “The Colombians have to come up with different strategies.”

But both presidents affirmed a strong commitment to the plan.

Human rights advocates had hoped Bush would put more public pressure on Colombia. A State Department report released last Tuesday indicated that while conditions have improved, “forced disappearances” persist, as do murders by security forces, corruption, and collaboration between soldiers and drug traffickers and terrorists.

The presidents also discussed the plight of three U.S. military contractors who have been held hostage by the Revolutionary Armed Forces of Colombia for four years. The men were on a drug surveillance flight when their plane crashed in a remote, rebel-controlled area in southern Colombia. Uribe has refused to trade the hostages for imprisoned guerrillas.

Bush sidestepped a question about whether a rescue operation is being considered.

“I am concerned about their safety,” he said of the captives.

“These are three innocent folks who have been held hostage for too long. … We hear from their families. Their kidnappers ought to show some heart.”