More than 100 countries on Friday challenged Security Council powers to restrict their use of the veto as the United Nations turned 70, with a joint pledge not to oppose resolutions on 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 Bashar al-Assad.
With 104 countries on board including Security Council permanent members France and Britain, the "code of conduct" won backing from a majority of the UN's 193 member states.
Supporters of the drive have lobbied countries for months to sign on to the pledge and pointedly announced the outcome on the 70th anniversary of the United Nations.
Under the measure, countries commit "not to vote against a credible draft resolution" that seeks to end or prevent genocide, war crimes or crimes against humanity.
The code of conduct leaves it to UN Secretary-General Ban Ki-moon to determine when an outbreak of violence could lead to mass atrocities.
Other than the five permanent members, the Security Council has 10 non-permanent members elected for two-year terms who vote on resolutions but have no veto power.
Australia, Germany, Italy, Spain and Mexico were also among the pledge signatories, as well as three of the countries set to take up non-permanent seats in January: Japan, Ukraine and Uruguay.
The code was drafted by a group of countries known as the Accountability, Coherence and Transparency group, led by Liechtenstein.
Their campaign chimes with a separate French proposal to restrict the use of the Security Council veto in cases of mass atrocities.
France's idea has won support from 73 countries, but is rejected outright by Russia while China and the United States have reacted coolly.
- Veto use offends -
Human rights groups have applauded the initiative, even though they are realistic about prospects for persuading the big powers to curb their use of the veto.
"It may provide a challenge to the misuse of the veto by some permanent members, a misuse that rightly offends so many UN member states," said Richard Dicker, Human Rights Watch's director for international justice.
"The code could increase the political costs of voting against a credible Security Council resolution in situations of mass atrocity crimes."
The veto power accorded to the P5 dates back to the UN's foundation, but calls to re-think its use have mounted.
Russia and China used their veto power last year to block a resolution asking the International Criminal Court to investigate crimes committed in Syria.
Russia's UN envoy Vitaly Churkin last month dismissed calls for restricting use of the veto as "populist" and said such a proposal was not realistic.
Churkin argued that declaring that mass atrocities have occurred could become a political tool, and raised questions about who would be empowered to make that determination.
Russia and its predecessor the Soviet Union have used their veto 81 times, while the United States has resorted to the measure 77 times, some 30 of those on Israeli-Palestinian issues alone.
Britain has used the veto 32 times, France 18 and China nine times.