President Hugo Chavez (search) on Sunday vowed to freeze oil exports to the United States and wage a "100-year war" if Washington ever tried to invade Venezuela (search).

The United States has repeatedly denied ever trying to overthrow Chavez, but the leftist leader accuses Washington of being behind a failed 2002 coup and of funding opposition groups seeking a recall referendum on his presidency.

Chavez accused the United States of ousting former Haitian President Jean-Bertrand Aristide (search) and warned Washington not to "even think about trying something similar in Venezuela."

Venezuela "has enough allies on this continent to start a 100-year war," Chavez said during his weekly television show.

He added that "U.S. citizens could forget about ever getting Venezuelan oil" if the United States ever tried to invade.

Venezuela provides about 15 percent of U.S. oil imports, but relations between the two countries are rocky over Chavez's friendship with Cuban President Fidel Castro, his criticism of U.S.-led negotiations for a free trade zone in the Americas and his opposition to the war in Iraq.

The United States was slow to condemn the 2002 coup, initially accusing Chavez of provoking his own downfall.

Chavez has increasingly railed against U.S. meddling in Venezuelan affairs as his opponents step up protests to demand the recall vote.

On Saturday, at least 500,000 Venezuelans marched in Caracas to protest the National Elections Council's ruling last week that an opposition petition for the recall vote lacked enough valid signatures. Opponents turned in more than 3 million signatures Dec. 19, but the council ruled only 1.8 million were valid. The council ordered more than 1 million citizens to confirm they signed and rejected more than 140,000 signatures outright.

Rioting over the decision killed eight people and hurt scores more. The violence subsided after the Organization of American States and the U.S.-based Carter Center pledged to help give citizens a fair chance to prove they signed.

Venezuela is deeply divided between those who fear Chavez is trying to impose Cuba-style socialism and those who say he has given an unprecedented political voice to the impoverished majority.

Chavez insists the recall petition is fraud-ridden. He claims many signatures belong to dead people, minors and foreigners.

On Sunday, Chavez promised his government would investigate the deaths and injuries from last week's violence. Opposition leaders accuse National Guard troops of committing abuses while trying to keep rock-throwing protesters from blocking roads with burning tires. Chavez accuses his opponents of instigating chaos.

"The government is investigating all the acts of violence and especially those in which people died," Chavez said. "Violence only takes place when a group of the opposition leaders decide there will be violence."