Brazilian President Dilma Rousseff has halted advance preparations for a state visit to Washington next month.
A statement from President Rousseff's office gave no reason for the cancellation. However, the announcement followed official demands for an explanation of allegations this week that the U.S. National Security Agency intercepted President Rousseff's communications.
The immediate effect of Thursday's action canceled a planned trip to Washington by an advance team of Brazilian officials preparing for the scheduled Oct. 23 visit.
Separately, President Barack Obama and President Rousseff met Thursday in Russia, on the sidelines of the Group of 20 economic summit in St. Petersburg.
No details of their conversation were immediately available, but Obama's adviser Ben Rhodes said the U.S. is working to resolve the dispute through "diplomatic and intelligence channels."
Rhodes told reporters at the summit: "We understand how important this is to the Brazilians. We understand their strength of feeling on the issue."
The disclosure of U.S. intercepts of Brazilian state communications came from documents copied illegally by Edward Snowden, a former NSA contractor.
An American-born journalist who lives in Brazil and is a confidant of Snowden's said this week that the NSA had access to the entire communications network of President Rousseff and her staff, including all telephone, Internet and social-network exchanges.
Without commenting on classified U.S. activities, White House adviser Rhodes said, "What we're focused on is making sure the Brazilians understand exactly what the nature of our intelligence effort is."