M23 rebel forces have poured into Goma in the eastern Democratic Republic of Congo.
There is anger that UN forces did nothing to stop the rebels moving into the town, the capital of the mineral-rich province of North Kivu.
In New York, the UN Security Council has voted unanimously for a resolution demanding sanctions on two of the rebel leaders.
France is leading the diplomatic drive and says calls for UN troops to fight are not appropriate.
“From the outside it looks a bit strange that you have soldiers who don’t fight, but UN forces, UN blue helmets are not parties in a civil war. They are not supposed to do the job of the national army.” said France’s Permanent Representative to the UN, Gerard Araud.
Insiders say the resolution is meant as a warning to regional players not to get involved in the conflict. But human rights groups want the UN to go further and name those backing the rebels. Experts say there is very strong evidence of support from Rwanda, something Kigali denies.