Venezuelan President Hugo Chavez expelled the U.S. envoy to Caracas and threatened to halt crude exports to the United States in case his government is attacked, in an act of solidarity with his country's ally Bolivia.

"Starting at this moment the Yankee ambassador in Caracas has 72 hours to leave Venezuela," Chavez said at a public event in the port city of Puerto Cabello, 120 kilometers west of Caracas.

He said it was "in solidarity" with the leftist government of President Evo Morales in Bolivia, which on Wednesday ordered the U.S. ambassador to La Paz to leave. Washington late Thursday expelled Bolivia's ambassador to the United States.

The U.S. State Department said it had not been officially notified of the expulsion.

Chavez then threatened to halt the supply of oil to the United States, its main client, if Washington attacks his government.

"If there is any aggression towards Venezuela" from Washington, "there would be no oil for the people of the United States," said Chavez, who used coarse expletives to disparage the U.S. government.

Also Thursday Chavez announced that his government had uncovered a coup plot hatched by active and retired military officers, which he said had tacit U.S. approval.

A military prosecutor said two officers -- retired general Wilfredo Barroso and retired major Elimides Labarca Soto -- will be tried for incitement to rebellion, a charge punishable by five to 10 years in prison.

At least eight other officers were detained in connection with the plot and were being interrogated, the prosecutor said.

Venezuelan public television aired a recorded conversation allegedly between three high-ranking retired military officers discussing plans to storm the presidential palace in Caracas, target Chavez, and blow up the presidential airplane.

"We have already detained several people," Chavez said.

The United States has rejected the allegations by Chavez and Morales. It retaliated against Bolivia on Thursday by ordering its ambassador to Washington to leave. Chavez told his own ambassador to the United States to come home before he was thrown out.

Chavez was briefly ousted in a 2002 coup that was initially welcomed by Washington. Even after the coup Chavez did not go so far as to expel the U.S. ambassador.

Chavez is the most radical of a growing number of leftist governments in Latin America that to a greater or lesser degree oppose Washington's traditional dominance in Latin America.

Venezuela has some of the largest oil reserves outside the Middle East and despite Chavez's clashes with the Bush administration, is a major supplier to the United States, which is its biggest customer.