The government over the weekend announced a timetable for the move to democracy, which includes a constitutional referendum in May, and multi-party elections in 2010.
On Tuesday Senior General Than Shwe, Myanmar's military chief, accused "subversive elements" of trying to split the country.
"They are imposing sanctions against the nation to create a large-scale disruption to national progress," he said in a statement read out by another military official on national television.
Than Shwe said political dissidents were "driving a wedge among the national races, misleading the people, and aiding and abetting anti-government groups" to weaken Myanmar.
He appealed to the 53 million people to "make endeavours for the emergence of an enduring State Constitution".
Critics say Myanmar's government is just trying to deflect attention from last year's brutal crackdown on pro-democracy protests.
The main opposition National League for Democracy party is expected to make its position clear later during the day.
Myanmar has been under military rule since 1962.
The United States, which is pushing for sanctions against the military government, says the referendum will be a sham conducted in a "pervasive climate of fear", and that no referendum held under such conditions "can be free, fair or credible".
The United Nations was more cautious in its response of welcoming the prospect of elections.
Ban Ki-moon, the UN secretary-general said the process should be more transparent and inclusive.
He urged the military to allow Ibrahim Gambari, the UN special envoy, for another round of talks with opposition leader Aung San Suu Kyi, who has been under house arrest for much of the last 18 years.
But the charter has already been rejected by the "88 Generation Students", a group of leading dissidents from a failed 1988 uprising.
They urged people not to endorse the charter, saying it was an attempt by the generals to legitimise their iron grip on power.
The underground All Burma Monks Alliance, which played a role in last September's pro-democracy protests, also rejected the charter and vowed to "keep on fighting by all means in order to help the entire people get over poverty and destitution".
The UN says more than 1,100 people are still being detained on account of their political or religious beliefs, and hundreds more have sought refuge in neighbouring countries.