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Brazilian President Dilma Rousseff canceled a trip to Washington by a team of aides preparing for her scheduled visit to the U.S. next month and was expected to discuss the matter with President Barack Obama at a summit in Russia, officials said Thursday

The cancellation of Rousseff's advance team visit is a further sign of the escalating tension with the U.S. over a Globo TV report this week that the National Security Agency's massive spy program directly targeted the communications of Rousseff and her top aides.

Rousseff, while weighing canceling her U.S. visit, is still scheduled to travel to Washington in late October. She was given the only invitation for a full state dinner scheduled this year, an honor meant to demonstrate the growing importance of Latin America's largest nation and a particular nod to Rousseff, whose foreign policy since taking office on Jan. 1, 2011, has been more U.S.-friendly than her predecessor's.

The Globo report that aired Sunday was based on NSA documents leaked by Edward Snowden to U.S. journalist Glenn Greenwald, who lives in Rio de Janeiro and worked with the network on the story. Most of Greenwald's stories on the NSA program have been published in Britain's Guardian newspaper.

The report said the U.S. agency mapped out the aides with whom Rousseff communicated and tracked patterns of how those aides communicated with one another and also third parties, according to a June 2012 NSA document. Greenwald said the document, while not containing excerpts of Rousseff communications, made it clear that U.S. officials were reading her emails and text messages.

Michael Shifter, president of the Washington-based Inter-American Dialogue, said the "distant but cordial" Brazil-U.S. relationship was under threat.

"These revelations are a major blow for the effort to increase trust between the two nations," Shifter said. "To sustain that effort the Obama administration needs to be less dismissive and more forceful and public about the outrageous NSA practices."

He added that it "would be a pity if this situation is not handled well and leads to a deterioration in U.S.-Brazil relations. If that happens, both countries would lose."

Officials at the U.S. Embassy in Brasilia declined to comment on the NSA case or cancellation of the advance team trip to Washington.

Obama's deputy national security adviser, Ben Rhodes, said in St. Petersburg that he had no information about whether Obama or the White House had been informed that Rousseff was canceling the advance team's trip.

But he noted that Rousseff and Obama sat next to each other Thursday at one of the sessions during the Group of 20 summit in Russia.

Earlier Thursday, as Obama flew to St. Petersburg, Rhodes told reporters that Obama would discuss the NSA issue with Rousseff during the summit and that the U.S. would also work through diplomatic and intelligence channels to respond to Brazil's concerns.

"We understand how important this is to the Brazilians. We understand their strength of feeling on the issue," Rhodes said. "We will work with the Brazilians so they have a better understanding of what we do and don't do, and we have a better understanding of their concerns."

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Associated Press writers Josh Lederman in St. Petersburg and Marco Sibaja in Brasilia contributed to this report.