President Bush hailed "extraordinary political and economic change" in the Western Hemisphere as he kicked off a five-nation South American visit Monday. He vowed not to let his tour be interrupted by military turmoil in Argentina.

In an appearance before a joint session of the Brazilian Congress, Bush praised Brazil for being among the first countries to impose economic sanctions against Iraq. He said the high oil prices resulting from the Persian Gulf crisis are costing Brazil $5 billion annually. Local experts, however, said Bush's figure seemed excessive."I realize the sacrifices that Saddam (Hussein's) brutality has caused this nation," Bush said, departing from his prepared text. Bush earlier had discussed with President Fernando Collor de Mello the impact on world oil prices and the global economy of Iraq's takeover of Kuwait.

In his speech, Bush hailed the "extraordinary political and economic change that is transforming the face of this hemisphere."

He described Brazil as a leader in this effort, citing Collor's efforts at reducing the size of the state, privatizing enterprises, combatting inflation and liberalizing trade. These steps, he said, "are the keys to growth and prosperity in the global economy of the 21st century."

He added: "To fulfill the new world's destiny, all of the Americas and the Caribbean must embark on a venture for the coming century: To create the first fully democratic hemisphere in the history of mankind."

There were no urgent issues to be discussed on Bush's agenda, but he wants to associate himself with what he sees as a rare opportunity in hemispheric relations. The first four countries on Bush's itinerary - Brazil, Uruguay, Argentina and Chile - all were under military rule within the past few years and now have elected governments. The fifth country, Venezuela, has been democratic since 1958. Bush is making the trip at a time of unusual harmony in U.S.-Latin American relations.

The centerpiece of Bush's policy toward Latin America is the Enterprise for the Americas Initiative, which is designed to achieve economic growth through expanded trade and investment and reduced debt.

The South American tour was to have taken place in September but was postponed because of the Persian Gulf crisis. Secretary of State James A. Baker III stayed behind in Washington to deal with that issue.

As the president arrived in Brazil at dawn, Argentine Nationalist officers seized army headquarters at Buenos Aires. Bush, scheduled to visit Argentina on Wednesday, told reporters, "I have no thoughts of changing my plans. I have great confidence in the security there."