That call was echoed by the US state department, which also condemned the detention of other Myanmar activists, saying it showed the military government had "renewed its assault on human rights".
Earlier in the week the Association of South-East Asian Nations (Asean), of which Myanmar is a member, took the unusual step of calling for Suu Kyi's release.
Asean has a long-standing policy of non-interference in members' internal affairs and usually shies away from any comments that could be taken as criticism.
"We have made these calls repeatedly, and Myanmar has found it difficult to respond," said Imron Cotan, the head of the Indonesian delegation at a meeting of senior Asean diplomats on Tuesday.
1988: Military crackdown on pro-democracy protests, est. 3,000 killed
1989: Aung San Suu Kyi sentenced to house arrest for allegedly endangering the state
1990: NLD wins landslide in national election, military refuses to recognise result
1991: Suu Kyi awarded Nobel Peace Prize
1995: Suu Kyi freed, but movements restricted
1997: Myanmar admitted to ASEAN
2000: Suu Kyi sentenced to house arrest for defying travel restrictions
2002: Suu Kyi released following UN-facilitated secret talks with govt
2003: Govt unveils "road map" to democracy; Suu Kyi returned to house arrest after her convoy is attacked in north of country
2005: Govt announces shift to new capital Naypidaw
2007: Nearly 3,000 prisoners released in amnesty to mark independence anniversary, no key political figures freed
Most Asean diplomats expected the government of Myanmar - formerly known as Burma - to extend her detention for another year, as it has done annually for the past three years.
At a ceremony launching the US senate's Women's Caucus on Burma on Wednesday, Bush said the senators would be writing to the secretary-general of the United Nations urging him to step up pressure on Myanmar.
In a rare intervention in foreign policy matters, the US first lady also urged China to "stand with us" in calling for Suu Kyi's release.
China, which has close military and economic ties with the military government, has said it will not get involved in Myanmar's internal affairs and has vetoed past United Nations resolutions condemning it.
Speaking alongside Bush, Democrat senator Dianne Feinstein said the mission of the newly established senate caucus was to "to shine a light on one of the most critical human rights situations in the world today".
She said the detention of Suu Kyi reflected the plight of all the people in Myanmar.
"The situation in Burma is not just about one woman," she said. "It's also about the treatment of a people who live under the fist of repression."
Suu Kyi has spent 11 of the past 17 years either in prison or under house arrest.
|Myanmar's military rulers have shown no |
indication of bowing to pressure [REUTERS]
Her current spell in detention began in May 2003 after she and other members of her party, the National League for Democracy (NLD), were attacked by what human rights groups say was a government orchestrated mob.
In recent days Myanmar authorities have arrested several activists who have held prayer vigils for her release, as well as others who have protested over the country's economic conditions.
NLD officials say at least 60 activists have been arrested in the past week for holding prayers calling for the 61-year-old opposition leader to be freed.