PORT OF SPAIN (Reuters) - U.S. President Barack Obama on Friday greeted and shook hands with Venezuelan President Hugo Chavez in an impromptu meeting where the anti-U.S. leader told him: "I want to be your friend."

Photographs released by the Venezuelan government showed Chavez, a fierce foe of former President George W. Bush, smiling warmly and clasping hands with Obama at the start of the Fifth Summit of the Americas in Trinidad.

"We shook hands like gentlemen. It was obvious it was going to happen," Chavez told reporters after the opening of the summit in Port of Spain. "President Obama is an intelligent man, different from the previous one."

Relations between OPEC member Venezuela and its key oil client the United States have been frayed since Chavez came to power and positioned himself as Cuba's closest ally and a standard-bearer for anti-U.S. sentiment in Latin America.

Obama met the Venezuelan firebrand at the start of his first encounter with Latin American and Caribbean leaders, where he reached out to the Americas by offering a possible new beginning with former Cold War foe Cuba.

A senior U.S. official said Obama initiated the encounter, walking across a room where leaders were lining up ahead of a welcoming ceremony to introduce himself to Chavez.

The official said Obama did not respond verbally to Chavez's comments.

"President Obama simply smiled and went back to his place in the line," the official said.

Chavez became one of the U.S. administration's most strident critics, criticizing Bush as a drunk and "the devil." In March, he said Obama was at best an "ignoramus" after the U.S. leader said Chavez had obstructed progress in Latin America.

The Venezuelan leader has often accused U.S. officials of trying to topple him since he survived a coup in 2002. Chavez expelled the U.S. envoy to Caracas in September after accusing Washington of meddling in the affairs of ally Bolivia.

The former soldier says socialist revolution can counter U.S. free-market policies in South America. But Washington has branded him a threat to regional stability who is trying to undermine democracy.

(Additional reporting by Jeff Mason; Writing by Patrick Markey)