The 193 UN members on Wednesday pored over the last "take it or leave it" draft of a treaty to regulate the conventional arms trade as marathon talks came to an end.
The president of the negotiating conference, Australian diplomat Peter Woolcott, gave UN members until Thursday to consider the draft hammered out in nine days of marathon talks.
"I will not consider further amendments. It is take it or leave," Woolcott told the conference as he presented the draft to be scrutinized by governments, particularly in the major arms producing nations.
It was not immediately clear whether any country would block the required consensus or disassociate themselves from Woolcott's proposed text.
While diplomats expressed cautious optimism, if there is not an agreement by midnight on Thursday, seven years of efforts to agree the first treaty on weapons ranging from side pistols to combat aircraft will collapse.
The treaty would aim to force countries to assess whether the sale of a weapon or component could be used for genocide, war crimes or by terrorists or organized crime gangs.
Non-government lobbying groups and many countries are disappointed that ammunition is not subject to the full controls applied to weapons. But the United States had made it clear it would not accept ammunition controls.
China and Russia also had concerns about the reporting of arms sales and whether weapons given as part of cooperation accords would be included.
The latest version of draft only encourages countries to make public efforts made to control arms sales. Any annual report on arms sales can be edited to keep confidentiality.
Amnesty International is "disappointed" that despite concerns expressed by many governments "the scope of the treaty remains short of what types of arms should be covered," said Brian Wood, the group's arms control specialist.
But he predicted the treaty would be adopted on Thursday.