More than 100 countries have challenged world powers to stop using their United Nations Security Council veto power on matters involving mass atrocities.
The initiative is aimed at avoiding the kind of gridlock that has paralyzed the Security Council on Syria, with Russia and China vetoing any attempt to sanction the regime of President Bashar al-Assad.
With 104 countries on board including Security Council permanent members France and Britain, the "code of conduct" has backing from a majority of the UN's 193 member states.
Only the five permanent members of the Security Council have veto power, however, and three have not embraced the measure.
The measure calls on countries to commit to voting for resolutions that seek to end or prevent genocide, war crimes, or crimes against humanity.
The UN Secretary-General would determine when an outbreak of violence could lead to mass atrocities.
A separate French proposal to restrict the use of the Security Council veto in cases of mass atrocities has won support from 73 countries, but has been rejected outright by Russia. China and the United States have reacted coolly.