"It is the height of national shame for the armed forces of any country to turn its arms against its own people," said Vivian Balakrishnan, repeating that Singapore was appalled by the violence against civilians in the country.
The United Nations has said at least 54 people have been killed since the Feb. 1 coup. More than 1,700 people had been arrested, including 29 journalists.
Balakrishnan and his counterparts in the Association of Southeast Asian Nations (ASEAN) had held talks with a representative of the junta earlier this week.
Singapore along with a number of other ASEAN foreign ministers have called for the release of political detainees including civilian leader Aung San Suu Kyi.
Balakrishnan said on Friday the foreign ministers were in daily contact with each another over Myanmar.
However, he said that while ASEAN should play a constructive role in facilitating a return to normalcy and stability, there would be s limited impact from any external pressure on the situation in Myanmar. "If you look over the past 70 years, the military authorities in Myanmar, frankly, do not respond to economic sanctions, do not respond to moral opprobrium," the Singapore minister said.
He said that while references to the ASEAN charter and human rights declaration were essential, they were not sufficient to change the junta's behavior.
"The keys ultimately lie within Myanmar. And there's a limit to how far external pressure will be brought to bear," Balakrishnan said.