By Helen Murphy
CARTAGENA, Colombia (Reuters) - Colombian President Juan Manuel Santos is using this weekend's Summit of the Americas to raise his profile on the world stage and showcase his nation's emergence from decades of drug-fueled rebel violence to become a Latin American investment magnet.
The event in Colombia's historic Caribbean coastal city of Cartagena will include regional heads of state and U.S. President Barack Obama on his first trip to the Andean nation. Santos and Obama are due to meet on Sunday.
Colombia has long been the closest U.S. ally in the region, and has often maintained strained ties with leftist neighbors.
But the Harvard-educated Santos, who came to power in 2010, has improved relations with Venezuelan counterpart Hugo Chavez and put Colombia on course to become a diplomatic conduit between the United States and Latin America's leftist governments. Under Santos, Colombia may assume a regional mediator role usually reserved for South American giant Brazil.
"Santos will come out of this very much strengthened as an international figure," said Colombian political analyst Elisabeth Ungar, referring to the summit. "He has positioned himself very strongly, not only in the region but in the wider international context."
The fact that Santos is even able to host such a high-level event illustrates the security advances that Colombia has made over the past decade and the improvement in his nation's previously dismal relations with much of the region.
His predecessor President Alvaro Uribe left office with his regional diplomatic standing in tatters. But it was Uribe's success against Marxist rebels that paved the way for Colombia to emerge from dark decades when it was best known as a quagmire of cocaine cartels, kidnappings and car-bombings.
Though he is still struggling to defeat the remnants of the guerrilla insurgency, the decade of sustained security gains could give Santos an influential voice on the war on drugs in Mexico and Central America, analysts say.
BURY THE HATCHET
Santos' first major action as president was to bury the hatchet with Chavez after years of poor relations between their countries, a history of many insults between the pair, and their diametrically opposed political ideology. He even called Chavez - a fierce critic of the United States - his "new best friend."
Colombia's leader then moved to improve relations with Venezuela's ally Ecuador, putting him in a good potential position to warm up relations between the leftist ALBA bloc of nations, which includes Bolivia, Cuba, Venezuela and Ecuador, and more conservative nations around the region such as Chile.
Santos knows that the war with the rebels is not fully over.
Thousands of Colombian troops, backed by robots searching for explosives, will sweep Cartagena in a reminder that drug-funded FARC rebels plotted assassination attempts against two U.S. presidents, Bill Clinton and George W. Bush, during past visits to the country.
Santos will also use this weekend's gathering to try to dazzle some 500 corporate chief executives who will attend a parallel business summit at which Colombian pop singer Shakira will speak. The meeting is set to focus on expanding the region's mining, manufacturing and retail sectors responsibly.
The meeting highlights the growing importance of foreign investment for Colombia, and contrasts sharply with the state takeovers and the forced renegotiations of private companies' mining and oil contracts seen in leftist Latin American nations such as neighboring Venezuela.
Colombia attracted a record $13.2 billion in foreign direct investment last year, mostly into its oil and mining industries.
Even before it began, the summit provided a tough test of Santos' new regional diplomatic ambitions.
Santos made a one-day visit to Havana last month to neutralize a threat by socialist leaders to boycott the meeting over U.S. insistence that Cuba not attend. Only Ecuador's Rafael Correa has said he will not attend.
In pursuit of a stronger regional profile, Santos would like to use the summit to demonstrate that he can mediate effectively in Latin American conflicts such as a long-running border dispute between Bolivia and Chile. He has even offered to help negotiations between Israel and the Palestinians.
The president does not have an unblemished record: he was a hardline defense minister under Uribe when security forces were accused of widespread human rights abuses, including killing villagers. And the summit is not risk-free for him either.
With the agenda likely to include thorny disputes such as the legalization of narcotics, Argentina's claim on the Falkland Islands and Cuba's participation in the next Summit of the Americas, Santos faces a delicate balancing act.
"The summit will be dominated by the issue of Cuba," said Vicente Torrijos, political science professor at the University of Rosario in Bogota. "That's a far cry from what Colombia had originally envisaged for its show of leadership."
(Additional reporting by Luis Jaime Acosta in Bogota; Editing by Daniel Wallis and Will Dunham)