"The devil came here yesterday," Chavez said, referring to Bush's address at the UN assembly on Tuesday.
"He came here talking as if he were the owner of the world."
The leftist leader, who has joined Iran in opposing US influence, accused Washington of "domination, exploitation and pillage of peoples of the world."
"We appeal to the people of the United States and the world to halt this threat, which is like a sword hanging over our head," he said.
Chavez also said the UN in its current entity was unworkable and "anti-democratic." He said the US government's 'immoral veto' had allowed Israel’s recent air strikes on Lebanon to continue unabated for over a month.
"Venezuela once again proposes today that we reform the United Nations," he said. He drew nervous laughter on occasion from the audience, but also some applause when he called US "imperialism" a menace.
Chavez criticised the US government for trying to block Venezuela's campaign for a rotating seat on the UN Security Council. He said Venezuela would be "the voice of the Third World" if US favourite Guatemala was chosen in a secret-ballot UN vote next month.