By REUTERS
 
CARACAS, Venezuela, April 24 (Reuters) - Venezuela is ending military operations and exchanges with the United States, President Hugo Chávez said Sunday, and he ordered out American instructors who he said had been trying to foment unrest in the barracks against him.

The end of military cooperation amounted to a further downgrading of ties between Venezuela, the world's No. 5 oil exporter, and its main oil customer, the United States.

Warning of what he called a possible American invasion of Venezuela, Mr. Chávez said a female United States naval officer and some American journalists were temporarily detained recently in separate incidents for photographing a Venezuelan Army base and an oil refinery.

Mr. Chávez, a leftist who often accuses Washington of working to oust him, said: "All exchanges with U.S. officers are suspended until who knows when. There will be no more combined operations, nothing like that."

Additionally, he said a small group of American military officers who were teaching and studying in Venezuela had been told to leave.

None of those evicted Americans were identified.

He was confirming a brief announcement by the United States Embassy on Friday that five Army, Air Force and Navy officers had received orders to end their missions in Venezuela.

"Some of them were waging a campaign in the Venezuelan military - making comments, talking to Venezuelan soldiers, criticizing the president of Venezuela," Mr. Chávez said in a television broadcast. "It's better for them to leave."

The United States Embassy, which said on Friday that it regretted Venezuela's ending of the 35-year-old military exchange program, did not comment Sunday about Mr. Chávez's televised remarks. American-Venezuelan relations have turned increasingly sour following a 2002 coup that briefly toppled Mr. Chávez and that he says was instigated and supported by Washington.

Bush administration officials deny this, but they call Mr. Chávez a troublemaker and criticize his growing arms purchases and alliances with countries like Cuba and Iran, which are enemies of Washington.

It was not clear whether the move would also end Venezuela's participation in multilateral antiterrorism and antidrug smuggling exercises involving American armed forces.

Mr. Chávez said an American had been arrested "a few months ago" taking photos of an army base in Maracay, west of Caracas.

"When her documents were checked - I have a copy - she turns out to be a U.S. naval officer," he said, without giving her name.

"If she or any other U.S. officer does this again, they'll be arrested and tried in Venezuela," Mr. Chávez said.

He added that the journalists, whom he did not identify, were freed after they had been seen photographing El Palito oil refinery in Carabobo State. It was unclear why such photography was not permitted.

Other than the marines who guard the American Embassy here, the United States has 13 defense attachés in Venezuela.

Ninety Venezuelan officers are attending courses in the United States. Mr. Chávez did not say if the end of military exchanges applied to them.

Opponents of the president, a former paratrooper, say he has slashed longstanding ties with the United States.

"You have to see this from a geopolitical point of view. We're no longer a country allied to the Western Hemisphere. We're going to be allied to China or Russia," a retired Venezuelan vice admiral, Rafael Huizi Clavier, told the newspaper El Universal in an interview published Sunday.