Her supporters have argued that she must now legally be either released or put on trial.
Extending her detention will likely provoke further criticism of the junta by an international community already frustrated by the military's handling of the relief effort after Cyclone Nargis.
The cyclone, which struck on 2 May, has left 134,000 people dead or missing and another 2.4m clinging to survival. Donors pledged nearly $50m (£25m) in aid at a landmark summit in Rangoon on Sunday.
The regime has been under fire for stalling foreign aid destined for cyclone victims.
Ms Suu Kyi's detention has long been the cause of friction between the junta and the international community.
Her party used the anniversary to denounce the regime's claim that 93% of voters had endorsed a new military-backed constitution at a recent referendum.
It said the vote was a "sham" that was not free or fair, and claimed the authorities "used coercion, intimidated, deceived, misrepresented and used undue influence" to boost the number of "yes" votes.
UN Secretary General Ban Ki-Moon speaks out against Aung San Suu Kyi's detention
The party also denounced the regime for holding the referendum so soon after Cyclone Nargis, saying the ruling generals only considered "power politics and self-interest", not public welfare.
Mr Ban, the UN secretary general, made his comments while briefing reporters about his recent trip to Burma, also known as Myanmar.
"The sooner restrictions on Aung San Suu Kyi and other political figures are lifted, the sooner Myanmar will be able to move towards inclusive national reconciliation, the restoration of democracy, and full respect for human rights," he said.
Mr Bush called for the release of all political prisoners, and for the military rulers to enter a "genuine dialogue" with pro-democracy and ethnic minority groups.
He said the US would continue to provide aid for Burma's cyclone victims, despite the decision, but it would also "support the Burmese people's long-term struggle for freedom".
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