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President George W. Bush renewed U.S. support to Colombia, a strong but drug and violence-plagued U.S. ally which receives more U.S. aid than any country outside the Middle East and Afghanistan.

Bush arrived in the nation's capital on Sunday to meet with President Alvaro Uribe in a show of confidence for Uribe and Colombia's battle against narcoterrorists. But the stop was clouded by a political scandal involving Uribe, and security jitters had Bush staying only about six hours.

Colombia was the third country on the president's five-nation tour of Latin America. He began his journey in Brazil, flew here from Uruguay and was headed later Sunday to Guatemala. Bush last stops in Mexico before returning to Washington Wednesday.

Despite close ties between Uribe and Bush, the U.S. president's visit has generated considerable criticism and strong protests. Police put down violent demonstrations here ahead of Bush's arrival.

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About a mile away from the presidential palace, some 1,000 protesters chanted "Down with Bush" and burned American flags. Friday night, a concert by former Pink Floyd frontman Roger Waters featured a big balloon of a pig that said "Patron Bush, Welcome to your Colombian Ranch."

It was Bogota's first visit from a sitting U.S. president since Ronald Reagan in 1982. Bush went in 2004 to coastal Cartagena, always deemed far safer than the capital of this country afflicted by a civil conflict for half a century.

Bush received a red-carpet greeting by a military honor guard when his plane landed. But some 20,000 police and heavily armed troops mobilized to prevent any rebel attack.

Sharpshooters were positioned on rooftops, the city center was shut down to traffic and Bogotanos had to do without their beloved "ciclovia," in which major avenues are given over on Sundays to biking, skating and jogging.

Bush rode to the palace on a route lined with gun-toting police standing guard every few feet, and his motorcade included white pickup trucks with local security officers filling the beds. Manhole covers were spray-painted to alert security agents to tampering.

"The security measures are excessive," said 56-year-old Manuel Cifuentes, who runs a food stand on the Plaza de Bolivar and said he hasn't had much business in the last few days.

The president has indicated he will ask Congress to maintain current aid levels to Colombia at roughly $700 million annually to support the Latin American nation's fight against terrorism and drug trafficking.

"The president looks forward to meeting with President Uribe to demonstrate U.S support for Colombia, highlight positive security and economic developments that have taken place there, and discuss the mutual commitment to the U.S. Colombia Trade Promotion Agreement," said White House spokesman Gordon Johndroe.

Johndroe also noted Bush would meet with Colombians involved in various U.S programs "that help them reap the benefits of a democracy as well as demonstrate the compassion of the American people."

Ahead of Bush's visit, the Colombian law-and-order president urged for continued aid, crediting the U.S. assistance with helping to make his violence-tortured nation more peaceful and less corrupt. The U.S. has sent nearly $4 billion in mostly military aid to Colombia since Uribe took office in 2002.

"I ask the world, I ask the United States, to support us. We haven't yet won but we are winning. And we will persist," Uribe said in an interview last week with The Associated Press.

But Democrats who now control the U.S. Congress have been asking tough questions about that aid.

Eight close Uribe allies in Colombia's Congress, as well as his hand-picked former domestic intelligence chief, have been jailed for allegedly colluding with right-wing militias in a reign of terror that nearly subverted Colombian democracy.

The scandal prompted Uribe's foreign minister to resign last month when her senator brother and father, a regional power broker, were implicated for alleged participation in the kidnapping of a political rival.

Many Democrats in the U.S. are expressing concern about Colombia's human rights record. They also want greater emphasis on social programs — more than 3 million have been displaced by the decades of fighting — and on bolstering an overtaxed justice system.

Colombia remains the source of more than 90 percent of the world's cocaine despite record aerial fumigation of coca crops. And the leftist Revolutionary Armed Forces of Colombia, or FARC, has neither been defeated nor had any members of its leadership captured.

The paramilitaries, which gained control of the entire Caribbean coast during the past decade, demobilized two years ago under a peace pact with Uribe's government. The paramilitaries arose in response to kidnappings and extortion by leftist rebels.

Bush and Uribe also were expected to discuss a U.S.-Colombia free-trade agreement now before Congress. Colombian demonstrators called for the scuttling of the pact, signed in November and currently stalled in Congress.

Meanwhile, three Americans have been held by rebels for more than four years in Colombia without the Bush administration taking routine steps toward freeing them, current and former U.S. officials say. Family members have cautioned the U.S. on a rescue attempt that could bring the hostages' deaths.

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