When Alvaro Uribe was first sworn in as president of Colombia in 2002 leftist rebels unleashed a shower of mortars on the presidential palace, terrifying visiting dignitaries and killing 21 homeless people in a nearby slum.

If there's no such repeat in Monday, when for the first time in more than a century a sitting Colombian president is sworn in for a second term, it will be the latest sign of the improving security in Colombia, where the murder and kidnapping rates are tumbling.

The falling crime rates and Uribe's hard line against leftist rebels helped him trounce his rivals in May's election.

He appears set to use his popularity to push an agenda including tax reform, more social spending and further pursuit of leftist guerrillas through a congress packed with supporters.

But Uribe, Washington's closest ally in Latin America, also faces stiff challenges trying to tame the four-decades-old insurgency and curb the world's largest cocaine industry.

There are signs that some in Washington are growing impatient after providing Colombia more than US$4 billion (€3.1 billion) in aid since 2000 for the fight against leftist guerrillas and drug traffickers.

In addition, Uribe's close ties with the U.S. administration of President George W. Bush has alienated some in South America, which has seen a wave of left-wing presidents take power, ranging from moderates such as Chile's Michelle Bachelet to outspoken U.S. critic Hugo Chavez in Venezuela.

"By getting so close to the White House, Uribe has deposited all his eggs in one basket," professor Bruce Bagley, chair of the Department of International Studies at the University of Miami and a longtime Colombia watcher.

This has brought concrete consequences, reflected in Colombia's complaints that it is not receiving full cooperation from its neighbors.

Colombia has said that leftist rebels cross the border unhindered into Venezuela and Ecuador. And according to authorities, the borders also are being used increasingly as transit zones for cocaine shipments.

Analysts note a growing restlessness in the U.S. Congress about how effective Colombia's efforts have been in the anti-drug fight and in its bid to modernize the army.

This year has produced a string of bad news in the war on drugs. Despite record fumigations, the land given over to growing coca, the raw material used in the production of cocaine, rose in 2005.

The army, meanwhile, is struggling with a series of scandals, including allegations of brutal hazing, the killing of innocent civilians, to accusations that a unit was bought by drug traffickers to kill anti-drug police agents.

And as the costly Iraq war drags on, there are fewer resources for the U.S. to give out. If Democrats gain control of the U.S. Congress in November elections they may be more reluctant to continue the wholesale backing of Uribe's efforts, analysts say.

"Uribe could be left hung out to dry," Bagley said.

Uribe has his critics at home, as well, worried that president's authoritarian rule has weakened Colombia's political institutions, noting how he rammed through congress a constitutional change to allow him a second term.

Uribe will have to be wary not to let popularity and power go to his head, said Michael Shifter, a senior fellow with the Inter-American Dialogue.

"There is a curse of the second-term, you have a lot of hubris, the arrogance of power, a move to a more personalized rule," Shifter said. "The history of second terms across the region has not been encouraging."

Meanwhile, the government isn't taking any chances with Monday's inauguration.

Seventeen helicopters patrol Bogota, eyeing this city of nearly 7 million from above. Rifle-wielding soldiers and mini-tanks stood sentinel at checkpoints on the city's roads, with some 30,000 soldiers and police patrolling the streets.