Burma's state media have published their first direct criticism of the democracy leader Aung San Suu Kyi since her release from house arrest.
The commentary said she and her party would "meet their tragic end" if they continued to endorse Western sanctions.
Aung San Suu Kyi was released from house arrest last November, after she and the NLD were excluded from the country's first elections in 20 years.
Burma now has a civilian government but the army still dominates parliament.
Commentary published in state-run newspapers accused Aung San Suu Kyi and the banned National League for Democracy (NLD) of "going the wrong way".
It said they had been "ignoring the fact that today's Myanmar [Burma] is marching to a new era, new system and new political platforms paving the way for democracy".
If they continued on this path they would "meet their tragic end", the writer warned, without giving further details.
The commentary also accused the NLD of being "big-headed" for sticking to "the weapon of sanctions until it gains power by demanding that any changes and modifications should be made in consultation with the party, let alone lifting the sanctions".
On a more conciliatory note, it invited Aung San Suu Kyi and the NLD to co-operate in building what it called a democratic nation, without saying what form this co-operation might take.
The criticism comes days after the NLD said it supported Western sanctions, but wanted talks on whether to modify them.
Burma's military rulers have long argued against sanctions, saying they hurt the people of Burma and have pushed the country deeper into poverty.
Since 65-year-old Nobel laureate Aung San Suu Kyi's release after two decades in nearly constant detention, the government has shown little reaction to her public appearances and speeches.
A veteran opposition politician told the BBC he believed the newspaper criticism was part of a new attempt by the government to suppress her and the NLD, which was forced to disband last year after refusing to participate in the elections.
The military has always maintained that November's elections were part of a roadmap to democracy in Burma, but they were widely dismissed as corrupt.