Ambassador Liliana Ayalde is a career diplomat with three decades of experience and a former ambassador to Paraguay. She most recently served as the deputy assistant secretary of state for Western Hemisphere affairs, covering Cuba, Central America and the Caribbean.
"This is a very important moment for our relations, full of opportunities and possibilities," Ayalde told reporters at Brasilia's airport, speaking in Portuguese. "I'm sure that together, we can expand and deepen the ties that exist between our two important nations."
The new ambassador didn't respond to Brazilian journalists' questions about the National Security Agency's spying program.
Ayalde arrives just as Brazilian President Dilma Rousseff is expected to make a decision on whether she'll cancel a trip to Washington next month in protest over the NSA program. She is scheduled to be honored with a state dinner, the only one scheduled so far this year in the U.S. for a visit meant to show Brazil's growing economic and strategic importance.
Several reports on Brazil's Globo television and in the Globo newspaper have been based on NSA documents leaked by Edward Snowden.
In addition to indicating that Rousseff's communications with her top aides were intercepted, reports say that the NSA targeted the private computer network of state-run oil company Petrobras and that the NSA has collected data on billions of emails and telephone calls that flow through Brazil.
Ayalde is also arriving in a nation shocked by huge anti-government protests in June. Demonstrations continue to linger and could be sparked again by a number of factors, including a slowed economy, next year's presidential election year and the World Cup. Many Brazilians are outraged at the billions of public funds being spent to refurbish or build stadiums while hospitals, schools and infrastructure widely remain in a woeful state.
Ayalde succeeds Thomas Shannon, who is now a counselor to Secretary of State John Kerry.