In Washington, the State Department urged coordinated international pressure on the Burmese military leaders and called the extension "unfortunate" and "condemnable."
The current European Union president, Germany, said it deeply condemns the move by Burma's rulers.
United Nations Secretary-General Ban Ki-moon also expressed regret over the decision. Mr. Ban said he "strongly believes" the release of Aung San Suu Kyi would help Burma to move toward national reconciliation.
Government sources say Burmese officials visited the Nobel prize laureate's residence Friday and read out the extension of her term. Her current four-year term of detention was up for review this Sunday.
Aung San Suu Kyi has spent most of the past 17 years under house arrest. Her National League for Democracy won the 1990 elections, but the government has prevented the party from taking office.
Rights activists say Burma's military leaders are more concerned about what might happen if Aung San Suu Kyi is released than about international pressure.
The activists argue that the government does not want or think it needs to have a dialogue with her to resolve its problems with the opposition.
Information for this story is provided by Reuters and AFP.