Suu Kyi, who has long looked to the West to bolster her efforts to promote democracy, voiced caution at the pace of reforms since the country began emerging in 2011 from almost a half-century of military rule.
"There have been times when the United States government has seemed over-optimistic about the reform process," she told reporters at her National League for Democracy party (NLD) headquarters in Yangon.
"This reform process started stalling early last year," she said, adding that she would question whether any major positive changes had happened "in the last 24 months".
Obama, who is also scheduled to meet Myanmar's former general turned-reformist leader Thein Sein, is likely to reiterate a call he made last week for "inclusive and credible" elections next year.
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Thein Sein's quasi-civilian regime has earned international plaudits and the removal of most Western sanctions in return for reforms, including releasing most political prisoners and allowing Suu Kyi and her party into parliament.
But the government has faced growing accusations that it has backtracked on rights issues in recent months, with journalists jailed in several high-profile cases and dozens of activists arrested.
But the veteran campaigner is currently barred from taking the presidency - a position appointed by parliament - because of a clause in the junta-drafted constitution.
This bars anyone with a foreign spouse or children from taking the top political office - a provision widely thought to have been written specifically to thwart her political rise.
Suu Kyi, 69, said she did not object to the clause because it blocks her political aspirations "but because it is intended to keep one particular citizen out of the presidency... A constitution should not be written with one person in mind".
Parliament has agreed to discuss the possibility of changing several parts of the constitution - including the provision that bars Suu Kyi - in debates expected to coincide with Obama's visit next week.