Iran and North Korea blocked an effort on Thursday to adopt a global treaty that would regulate the multimillion-dollar international weapons trade.
The draft treaty needed support from all 193 UN member states to be approved.
The delegate from North Korea said the proposed treaty could be "politically manipulated by major arms exporters."
Iran's UN ambassador Mohammed Khazaee said the proposed accord was "discriminatory."
Treaty supporters were optimistic before the vote, but said if it was not adopted they would go to the General Assembly and put the draft to a vote, where it is expected to be approved.
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"Signals are that the treaty stands a good chance of being adopted today," said Anna Macdonald, head of arms control at Oxfam, one of about 100 organizations worldwide in the Control Arms coalition. "There have been concerns that Iran might block, but we've heard ... that Iran is going to support it."
Chairman of the negotiations Ambassador Peter Woolcott of Australia called for a suspension of the final negotiation session after the Iran and North Korea block, hoping the delegates from the two countries could change their votes.
UN members looked over a "take it or leave it" draft of what would have been the first ever treaty to regulate the conventional arms trade.
Woolcott gave members the final draft on Wednesday after nine days of marathon talks.
"I will not consider further amendments. It is take it or leave it," Woolcott told the conference as he presented the draft.
If put into place, the treaty would make states establish standards in barring the sale of conventional weapons if they would lead to violations of international human rights law, or aid terrorism or organized crime. Weapons likely to increase violence against women and children would also be banned from sale.