(Adds context, OAS call for restoration of Colombia, Ecuador ties)

By Nelson Bocanegra

MEDELLIN, Colombia, June 3 (Reuters) - Venezuela on Tuesday accused the United States of trying to spread violence in the Andean region after a U.S. official said left-wing Colombian rebels were hiding in Venezuelan territory.

Colombia and the United States have long said Venezuela is not doing enough to combat Marxist FARC guerrillas waging Latin America's longest insurgency. New York-based Human Rights Watch called on Venezuela to clarify its relationship with the rebels, who are also deeply involved in drug trafficking.

Deputy U.S. Secretary of State John Negroponte on Monday urged Venezuela to crack down on rebels hiding on its side of the border. Venezuela's left-wing government, which has voiced solidarity with the rebels' goals, called Negroponte's statement "irresponsible and abusive."

"There is a campaign under way and we want to denounce it," Venezuelan Foreign Minister Nicolas Maduro told reporters. "The government of the United States is directly responsible for this campaign, which is intended to fill our region with violence."

Maduro, speaking at a meeting of the Organization of American States (OAS) in Medellin, Colombia, said Venezuela has not offered sanctuary to rebels who have been fighting the Colombian state for four decades.

Colombia, which has received $5.5 billion in mostly military aid from the United States over the last seven years, shares a 1,390-mile (2,237-km) border with Venezuela.

Tensions increased after a Colombian military raid into Ecuador in March that killed a rebel commander, Raul Reyes.

Colombian and U.S. officials say files and e-mails found on Reyes' computer indicate Venezuelan President Hugo Chavez and Ecuadorean leader Rafael Correa provided financial support to the rebels.

Both deny the charges and called the Colombian military raid a U.S.-backed violation of Ecuador's sovereignty.

SERIOUS QUESTIONS

"The e-mails raise serious questions about Venezuela's relationship with the Colombian guerrillas that deserve serious answers," said Human Rights Watch in a statement.

"At the very least, they appear to show that guerrilla commanders who were engaged in horrendous abuses believed they had the backing of the Venezuelan government," it said.

The rights group denounces FARC rebels for killing and kidnapping civilians and its use of land mines.

Colombia is Washington's closest ally in South America while Correa and Chavez are fierce critics of U.S. policy.

Ecuador has not reestablished diplomatic ties with Colombia since the March raid. OAS chief Jose Miguel Insulza on Tuesday called on the two countries to make progress toward reestablishing normal relations within two months. (Writing by Hugh Bronstein; Editing by Eric Walsh)

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