Brazilian President Dilma Rousseff's scheduled state visit to the United States may be in jeopardy after revelations that Washington spied on her, an official source told Efe Tuesday.

"The next steps will decide" whether Rousseff travels to Washington next month as planned, the source said.

The Brazilian government will make a determination based on the content of the written explanation it has demanded from the United States, he said.

Rousseff and U.S. President Barack Obama will both be in St. Petersburg, Russia, this week for the G20 economic summit, but there are no plans for a bilateral meeting, according to the source.

The U.S. National Security Agency intercepted telephone calls and e-mails of Rousseff and Mexican leader Enrique Peña Nieto, Brazil's Globo television said this week, citing documents from whistle-blower Edward Snowden.

Globo's flagship news magazine, "Fantastico," referred to a June 2012 "Top Secret" slide presentation touting NSA's ability to access the content of the voice and e-mail communications of both Rousseff and Peña Nieto.

The slides were among the documentation Snowden, a former U.S. intelligence contractor, provided to Brazil-based U.S. journalist Glenn Greenwald.

Brazilian Foreign Minister Luiz Alberto Figueiredo summoned U.S. Ambassador Thomas Shannon on Monday to discuss the Globo report.

"I made it clear that the violation of the president's communications is inadmissible, unacceptable, and constitutes a violation of Brazilian sovereignty," the minister said of his meeting with the U.S. envoy.

Figueiredo also told Shannon that Brazil wants a written explanation of the spying.

NSA's targeting of Rousseff "clearly exceeded the limit of the struggle against terrorism," Brazilian Justice Minister Jose Eduardo Cardoso said, referring to Washington's public rationale for pervasive global surveillance.

The Brazilian government was already uneasy about U.S. spying after O Globo newspaper reported in early July that NSA tapped into Brazil's telecommunications network via an unnamed U.S. telecom company that obtained access through one or more local partners.

O Globo, citing information from Snowden, also said the NSA and CIA maintained an intelligence listening post in Brasilia until at least 2002. EFE