However the delegation member Borje Ljunggren, a Swedish foreign ministry official, refused to disclose details of the discussions between the ruling generals and the National League for Democracy (NLD) led by the Nobel peace prize winner Aung San Suu Kyi.
He said they were "at a sensitive stage" and that nothing should be allowed to disrupt them while the two sides were still building confidence.
"We consider the talks to be the most interesting development since 1990," Mr Ljunggren said in Bangkok on arrival from the Burmese capital Rangoon, a reference to the only time the junta has allowed a free election. "We see our task as being supportive."
The NLD won more than 80% of the seats in the 1990 poll but the military immediately annulled the result and has sought to repress the NLD and Ms Suu Kyi.
In recent weeks, however, the demonising of the group in the local media has stopped and more than 80 NLD party activists, including deputy-chairman Tin Oo, have been released from prison.
The talks between the political opponents began in October, shortly after Ms Suu Kyi was banned from travelling outside Rangoon on party business. She has been held under virtual house arrest ever since. Mr Ljunggren, who held more than two hours of talks with Ms Suu Kyi at her home, said she was in good health
Analysts are unsure why the junta suddenly began talks with the NLD, particularly as the generals' grip is not thought to be slipping. A report by the International Crisis Group at the end of December described the regime "to be as strong as at any time in the country's history".
Bo Mya, vice-chairman of the Karen National Union, an organisation fighting for a Karen homeland along the Burmese-Thai border, said after meeting the visiting diplomats that the generals had little choice but to begin talks "because they are under pressure from all over the world".
Others believe the junta is driven by a desperate need for an end to international sanctions and renewed foreign investment. The parlous state of the economy was highlighted by a recent US government report which estimated that at least half of the government's income came from heroin.
