Burma's military government has been criticised by foreign leaders for its handling of constitutional talks.
US President George Bush said Burma was a threat to US interests, and extended economic sanctions for another year.
There were calls for the junta to free pro-democracy leader Aung San Suu Kyi and allow her NLD party to join the talks on constitutional reform.
The NLD has refused to take part due in the National Convention because of Aung San Suu Kyi's continued detention.
The military government claims the convention is a historic step towards democracy.
But analysts say it lacks credibility because of the absence of the NLD.
The opposition party decided to boycott the meeting after the junta refused to release Aung San Suu Kyi and vice chairman Tin Oo, both of whom have been detained since last May.
The government also turned down the party's demand that it reopen all of its offices before the convention. Currently, only the party's headquarters in Rangoon are open.
US President George Bush said Burma's "actions and policies are hostile to US interests, and pose a continuing unusual and extraordinary threat to the national security and foreign policy of the United States."
Mr Bush said that "to respond to this threat", he was keeping sanctions in place, and curbing investments in Burma for at least another year.
The European Union expressed "disappointment and concern" that Aung San Suu Kyi was still under house arrest.
Even the prime minister of neighbouring Thailand voiced rare criticism of Burma's military generals.
Thaksin Shinawatra said he was concerned over the lack of democratic
progress, and did not "not feel comfortable" about it.
"I am trying
not to intervene in their internal affairs but if you ask me
personally, I would like to see all parties included," he said.
"We understood they would release [Aung San Suu Kyi] in time to attend the
meeting," Mr Thaksin said of Burma's military rulers.
Japan and Malaysia both said a way must be found for the NLD to attend the constitutional talks, and UN Secretary-General Kofi Annan said the National Convention lacked credibility without the presence of Aung Sang Suu Kyi.
Ms Suu Kyi won a landslide victory in 1990, but was denied power by the military.