US president Bush, calling on countries to live up to freedoms and rights promised by the United Nations almost six decades ago, on Tuesday announced tighter sanctions on Myanmar and denounced the governments of Belarus, Cuba, Iran, North Korea, Syria and Zimbabwe as “brutal regimes” that should be confronted for their abuses.

In contrast to previous addresses here, he barely mentioned the wars in Iraq and Afghanistan except to say that the international community should do more to support those countries. Nor did he make a reference to one of his administration’s biggest foreign-policy concerns: Iran’s nuclear program.

Bush made his remarks at the opening of the 62nd session of the General Assembly, an annual gathering that was at points stormy and theatrical. Cuba’s foreign minister walked out of the president’s speech, protesters rallied outside with “Arrest Bush” signs and Mahmoud Ahmadinejad, Iran’s president, rebutted most of what Mr. Bush said.

Bush used his most forceful language to denounce countries that the United States publicly ranks among the least democratic. He also called on members of the United Nations to do more to support foundling democracies, later meeting with the leaders of several of them, including Georgia, Botswana, Afghanistan and Honduras. “Every civilized nation also has a responsibility to stand up for the people suffering under dictatorship,” he said.

In the case of Myanmar, Bush excoriated the country’s military government, which in the past few weeks has faced the most extensive public protests in nearly two decades. He outlined a tightening of economic sanctions in place since 1997 to aim at specific individuals for the first time. He also announced a ban on visas of those “responsible for the most egregious violations of human rights” and their families.