The European Union is set to impose new sanctions against Burma, according to the EU's Dutch presidency.
The Asem meeting is designed to build bridges
The EU warned last month that it would take action against Burma unless human rights improved before the Asia-Europe summit (Asem), which opens on Friday.
The Dutch foreign minister said the decision was set to be ratified at an EU foreign ministers meeting on Monday.
Leaders from 38 Asian and European nations are in Vietnam for the Asem summit, designed to strengthen ties.
China, Japan and South Korea, and the member-states of both the Association of Southeast Asian Nations (Asean) and the European Union are taking part.
Announcing the sanctions on Thursday, Dutch Foreign Minister Bernard Bot said: "I think it is... very important not only to give a political
signal to Myanmar [Burma] itself, but also to other countries participating
in this Asem meeting that the European Union does not condone this behaviour."
The new sanctions will extend the list of senior Burmese officials who are currently banned from gaining visas to visit Europe, as well as prohibiting European companies from providing finance to state-owned interests inside Burma.
Some EU states wanted to exclude Burma completely from this meeting, the first since the enlargement of both Asean and the EU.
They wanted the country's military rulers to release pro-democracy leader Aung San Suu Kyi from house arrest, and agree to several other reforms before it was allowed to attend.
But the Asean countries countered by saying that all three of their new members, Burma, Laos and Cambodia, must be included, or the EU's 10 new members must be excluded as well.
The result was an uneasy deal, whereby Burma would attend but only with a lower-level delegation, led by the newly-appointed foreign minister, Nyan Win.
Burma will not be the sole topic of conversation at the Asem meeting.
The Chinese government will again be pressing its demands for the lifting of the EU's embargo on arms exports to China, in place since the army's suppression of the Tiananmen Square pro-democracy protest 15 years ago.
The meeting's agenda covers a range of topics from free trade to co-operation against terrorism.
But the summit now risks developing into a clash of political values between Asia and Europe over Burma, where harsh sentences for peaceful protests and other human rights abuses were recently condemned in a report by experts of the United Nations.