Mr. Annan -- speaking through a UN spokesman -- noted Burma's recent decision to close a National Convention aimed at creating a new constitution until later this year.
The secretary-general also called on Burmese authorities to let the special UN envoy for Burma, Razali Ismail, back into the country as soon as possible.
Mr. Razali has not been allowed into Burma for more than a year.
Mr. Annan urged Burma to free all political prisoners and allow the offices of the National League for Democracy, a main opposition party, to re-open.
Information for this report is provided by AP.