Venezuelan President Hugo Chavez defended Iran's nuclear program Tuesday, saying Washington's firm opposition to Tehran and the invasion of Iraq both resulted from America's insatiable thirst for oil.

"You know that one of the most serious problems the world has today is the energy problem, so much so that the North American empire has invaded Iraq just to look for oil and now threatens Iran because of oil," Chavez said in a nationally televised speech, referring to the U.S. "It's an excuse by the empire, looking for energy."

Chavez, one of the most outspoken critics of U.S. foreign policy, claimed the Bush administration is falsely accusing Iran of trying to build an atomic bomb as a pretext for seizing control of the Middle Eastern nation's vast petroleum reserves.

"I'm completely sure that it's absolutely false that the Iranian government is developing an atomic bomb. It's the United States that has atomic bombs," Chavez said.

U.S. officials believe Tehran is using its nuclear energy program as a cover for producing an atomic bomb. They have criticized Venezuela's increasingly close ties with Iran that include projects such as a joint $200 million development fund.

Twenty-seven of the 35 members of the International Atomic Energy Agency, a U.N. nuclear watchdog, voted in January to refer Iran to the Security Council over fears it aims to build an atomic bomb. Venezuela, Cuba and Syria voted against it, and the rest abstained.

Chavez said developed countries such as the United States, France and Germany want to maintain a monopoly on nuclear technology by denying it to developing countries like his own.

Venezuela — the world's fifth-largest oil exporter — is studying the possibility of using nuclear power to generate electricity.

Chavez's comments came on the heels of another speech Monday night in which he warned that if U.S. troops were to invade any Latin American country, "revolutionaries" from across the region would join forces to battle the Americans.

Chavez's remark confirmed what many in Venezuela have long presumed: that his government would go to the aid of a close ally like Cuba in the hypothetical scenario of the U.S. sending troops.

Although U.S. officials dismiss his claims as outlandish and say they have no plans to attack Cuba, Chavez insists his country must be on guard to face any potential U.S. military attack.

The Venezuelan leader said the U.S. "should know that if it wants or someday decides ... to invade any of our countries — be it Venezuela, Cuba, Bolivia, El Salvador, Nicaragua, today, tomorrow or the next day — we would be there gathering together the revolutionaries to do battle with weapons in hand against U.S. imperialism."

The U.S. has accused Chavez of trying to export his socialist "revolution" to neighboring countries, saying he is a destabilizing force in the region.

Chavez argues he poses no threat, saying the U.S. is the one with a history of invading countries from Iraq to Panama.

Despite political tensions between Chavez's government and Washington, Venezuela still sells the largest share of its oil to the United States.

Chavez also lashed out Monday against Washington's efforts to promote free trade deals with Latin American countries.

The Venezuelan leader argues the U.S.-proposed Free Trade Area of the Americas would help transnational companies grow wealthier at the expense of Latin America's poor. He has joined Cuban President Fidel Castro in proposing a "Bolivarian Alternative" trade pact based on socialist principles rather than free-market competition.