U.S. President George Bush used his appearance before the United Nations General Assembly on Tuesday to criticize several governments, including Burma, against which he announced new sanctions.
Mr. Bush said the United States will tighten economic restrictions and expand a visa ban against Burmese leaders.
The U.S. leader also criticized Syria, Belarus, North Korea, Sudan and Iran for human rights violations. He called the behavior of Zimbabwean President Robert Mugabe's government "an assault on its people."
The Cuban delegation walked out during Mr. Bush's criticism of President Fidel Castro. Nicaraguan President Daniel Ortega later chastised Mr. Bush for his "lack of respect" toward Mr. Castro, and noted the U.S. had once tried to assassinate the Cuban leader.
In the French president's address to the assembly, Nicolas Sarkozy said Iran is entitled to nuclear power for civilian use, but that allowing Tehran to acquire nuclear weapons would pose an "unacceptable risk."
Earlier, U.N. Secretary-General Ban Ki-moon pressed world leaders to support changes throughout the United Nations, to better confront what he described as a "daunting array of challenges."
At today's opening of the General Assembly debate, Mr. Ban listed several of the high-profile challenges the world body faces -- from reducing the spread of weapons of mass destruction to countering climate change and poverty.
The secretary-general also said that Iraq had become "the whole world's problem."
Iranian President Mahmoud Ahmadinejad and German Chancellor Angela Merkel are among the other national leaders addressing the General Assembly today.
Venezuela announced today that President Hugo Chavez will not appear, a year after his speech to the Assembly in which he implied that Mr. Bush was Satan.
European, Russian, Chinese and U.S. officials negotiating with Iran about its nuclear program are planning to meet this week to discuss new sanctions against Tehran.
Nearly 100 presidents and prime ministers are attending meetings in New York City through Wednesday of next week.