President Barack Obama said on Sunday that Brazil's emergence as a powerful democracy was an example other nations could follow, as young people in the Middle East and north Africa rebelled for greater freedom.

"As two nations who have struggled over many generations to perfect our own democracies, the United States and Brazil know that the future of the Arab World will be determined by its people," Obama said to a standing ovation at a historic theater in downtown Rio de Janeiro.

Obama has ordered U.S. forces into the biggest military intervention in the Arab world since the 2003 invasion of Iraq, authorizing strikes against Libya on Saturday as he met with Brazilian President Dilma Rousseff in Brasilia.

"We've seen the people of Libya take a courageous stand against a regime determined to brutalize its own citizens. Across the region, we have seen young people rise up," he told an audience of about 2,000 prominent Brazilians in a speech that was televised live across Brazil.

"When men and women peacefully claim their human rights, our own common humanity is enhanced... That is the example of Brazil," he said to loud applause in the ornate hall.