Former Defense Minister Juan Manuel Santos swept to a landslide victory in Colombia's run-off election on Sunday to succeed President Alvaro Uribe as the leader of Washington's top ally in Latin America.

Santos, backed by conservative Uribe, had won 69 percent of the votes against former Bogota Mayor Antanas Mockus who trailed with 27.6 percent with more than 98 percent of polling stations counted, according to election authorities.

Santos has promised to stick to Uribe's security and pro-business policies, which have drawn in record levels of foreign investment. His victory will likely strengthen Colombia's peso, stocks and local TES bonds.

Uribe is still popular after two terms during which he battered left-wing FARC rebels and disarmed outlawed paramilitaries who once battled, bombed and kidnapped across Colombia, Latin America's No. 4 oil producer.

Santos received more than 8.8 million votes -- a record high for a Colombian president -- and will assume the presidency in August with a strong mandate and solid support in the country's Congress.

All I have to say is thanks, thanks and a thousand thanks, Santos, 58, said in a message on his Facebook page minutes after results showed his victory.

In a sharp reminder of the lingering conflict facing Santos, seven police officers were killed in a land mine blast near the Venezuelan border on election day, and troops killed six guerrillas in clashes in a central department.

Santos, who has also served as finance minister and helped Colombia over a 1990s fiscal crisis, must tackle double-digit unemployment, a stubborn deficit and a costly public health system as the economy recovers from the global crisis.

He's the most well-prepared person to lead this country, said Bernardo Escallon, a lawyer who voted in Bogota. Santos has all the solutions for Colombia's problems from security to the economy to health.

Tensions with Venezuelan President Hugo Chavez, who has cut trade in a dispute weighing on Colombia's economy, will also simmer on under Santos. The two men, who Santos says are oil and water, have clashed repeatedly.

SECURITY, SCANDALS, JOBS

A U.S.- and British-educated economist who began his public career in his mid-20s, Santos easily won a May 30 first round, falling just short of the 50 percent plus one vote he needed to avoid a run-off.

Mockus' small Green Party had challenged traditional parties with a call for cleaner government, but he was unable to stop Santos, who was closely identified with Uribe.

The Green Party will be an independent force, Mockus said, accepting defeat at his campaign headquarters. There are millions of us who have found a new way to do politics.

Since Uribe came to power in 2002, violence, kidnappings and bombings have dropped sharply thanks to billions of dollars in U.S. aid to fight guerrillas and drug barons. Now safer, Colombia is enjoying an oil and mining boom despite lingering violence from its cocaine-fueled conflict.

In February, a court blocked an attempt by Uribe supporters to change the constitution to let him run again. The ruling triggered a short, intense campaign to succeed the leader whose popularity rating hovers around 70 percent.

Uribe's second four-year term was marred by scandals over corruption and rights abuses, including arrests of lawmakers for colluding with death squads and a probe into state spies illegally wiretapping journalists and judges.

Santos, son of one of Bogota's elite families who is meticulous about his appearance, distanced himself from the scandals, portraying himself as an experienced technocrat and a results-driven manager.

As defense minister, he oversaw some of the sharpest blows to guerrillas. He also ordered a successful rescue operation to free prominent rebel-held hostages, including a former presidential candidate and three American contractors.

But his tenure was tainted by charges troops killed civilians to artificially lift combat tolls. The scandal cost the army chief and 27 officers their posts, but Santos said he worked to halt the so-called false positive killings.

Democrats in the U.S. Congress deciding on a U.S. free trade deal for Colombia will keep a sharp watch on Santos' government to see how he handles their concerns over threats against human rights observers and labor union leaders.

As head of Uribe's large U Party, Santos won the support of the Conservative and Cambio Radical parties after the first round and part of the opposition Liberal Party -- giving him a solid position in Congress.

(Additional reporting by Daniel Wallis, Alonso Soto and Javier Mozzo; editing by Kieran Murray and Mohammad Zargham)

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