Venezuela's leader Hugo Chavez has called US President George W Bush "the devil" in a speech at the United Nations General Assembly.
"The devil came here yesterday," he said, referring to Mr Bush's speech on Tuesday. "It still smells of sulphur today," he added.
US State Department spokesman Tom Casey said it was disappointing to see a head of state speak in such a way.
Mr Chavez went on to criticise the UN system, which he said was "worthless".
The left-wing Venezuelan leader - allied to Cuba's Fidel Castro and with growing ties to fellow oil-producer Iran - has long had tense relations with the US.
On Tuesday, Mr Bush had defended his policies on the Middle East and said democracy was gaining ground as terrorists were marginalised.
Mr Chavez, who brandished a copy of American leftist writer Noam Chomsky's Hegemony or Survival: America's Quest for Global Dominance, said Mr Bush promoted "a false democracy of the elite" and a "democracy of bombs".
"He came here talking as if he were the owner of the world," the Venezuelan leader said.
He called for drastic reform of the UN to reduce what he called US influence.
The UN in its current form "doesn't work", he said.
"I don't think anybody in this room could defend the system," the Venezuelan leader added.
The UN General Assembly is holding its 61st session
"Let's be honest. The UN system born after World War II collapsed. It's worthless."
Mr Chavez's criticism of the UN echoed Iranian President Mahmoud Ahmadinejad's speech to the assembly late on Tuesday, BBC diplomatic correspondent Bridget Kendall reports from New York.
"As long as the UN Security Council is unable to act on behalf of the entire international community in a transparent, just and democratic manner, it will neither be legitimate nor effective," Mr Ahmadinejad said in a speech delivered a few hours after Mr Bush's appearance.
Wednesday's session opened with a speech by Afghan President Hamid Karzai who argued military action alone would not stop terrorism in his country.
He called for the destruction of safe havens and elaborate networks operating in the region to recruit, train, finance, arm and deploy terrorists.
And he said the answer to defeating the drugs trade lay in international support for providing a "meaningful alternative livelihood to our farmers".
In other business at the General Assembly
- The US and the three other members of the so-called quartet of Mid-East mediators endorsed the idea of a Palestinian national unity government
- African Union leaders decided to extend the mandate of their peacekeeping force in Darfur until the end of the year
- The UN was due to hold a special meeting to discuss the four-year-old crisis in Ivory Coast, divided since its civil war.