By Andrew Gray

BOGOTA, Jan 17 (Reuters) - The top U.S. military officer said on Thursday he was concerned by Venezuelan President Hugo Chavez's purchases of military equipment, saying they could harm efforts to build greater stability in Latin America.

On a visit to Colombia, Navy Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, also dismissed the leftist president's claim to be the target of assassination plots by Washington and Bogota.

Chavez is a thorn in Washington's side and has clashed with Colombia over frontier security. Colombian President Alvaro Uribe is a top U.S. ally in South America and the U.S. military backs his campaign against cocaine-funded leftist guerrillas.

Mullen said he shared concerns that Colombian officials had shared with him about Chavez's plans for his military.

A former head of the U.S. Navy who took on the top U.S. military post October, Mullen mentioned both high-performance planes and submarines as items of particular concern.

"To the degree that those capabilities come into theater, they certainly are of great concern not just to Colombia... but to the region and in fact very much to the United States," he told reporters in Bogota.

Venezuela purchased 24 Sukhoi fighter jets and 100,000 Kalashnikov AK-103 assault rifles from Russia in 2006 and has talked about purchasing submarines, equipment Chavez says is needed to protect Venezuela from any "imperialist" attack.

The latest spat between Bogota and Caracas began when Chavez said Colombia's FARC and ELN guerrilla groups should not be treated as terrorists after he brokered the release of two hostages held by the FARC last week.

His call prompted Colombia to accuse Chavez of interfering in its affairs. Venezuela's Foreign Ministry accused the Colombian government on Thursday of being "obsessed with war".

Chavez said on Wednesday he had evidence of a plot by the United States and Colombia to kill him -- the latest in a long line of similar accusations he has made.

"They are unfounded accusations," said Mullen, making his first visit to Colombia.

"They are the kind of accusations that have been out there for a long, long time," he added. "Really from the United States' perspective, we don't pay much attention to them."

Colombian Defence Minister Juan Manuel Santos also dismissed Chavez's statement.

"If there is any proof... let him show it," Santos said at a joint news conference with Mullen. "These are baseless accusations that are repeated every so often and we do not attach any importance to them." (Additional reporting by Patrick Markey in Bogota; editing by Stuart Grudgings)

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