The 193 UN members pored over the last "take it or leave it" draft ahead of a crunch decision Thursday whether to agree the first ever treaty to regulate the conventional arms trade.
The president of the negotiating conference, Australian diplomat Peter Woolcott, on Wednesday gave UN members the final draft hammered out in 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 that is being given particularly close scrutiny by the major arms producing nations.
It was not immediately clear whether any country would block the required consensus required to agree a treaty on Thursday or disassociate themselves from Woolcott's proposed text.
While diplomats expressed cautious optimism, if there is not an agreement by midnight Thursday, seven years of efforts to agree on the first treaty on weapons ranging from side pistols to combat aircraft and warships will collapse.
Changes made since the start of the talks have made "significant improvements," said Britain's chief negotiator Joanne Adamson.
Adamson highlighted "a new article on preventing diversion of arms and (a) strengthened section on exports which are prohibited."
"It is not everything that we wanted, but it will be the first treaty on an industry that causes much suffering and there are benchmarks," said a European UN ambassador, speaking on condition of anonymity.
The treaty calls for national checks on arms sales on the international market that some groups estimate at being worth $80 billion a year.
The United States, Russia, Germany, France, China and Britain were the top six arms-selling nations in 2012, the Stockholm International Peace Research Institute said on the day the treaty talks started.
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.
"Reports may exclude commercially sensitive or national security information," said the latest text.
The British negotiator said that "human rights are at the heart of this text. With text, we should be able to meet our objective of a strong treaty with broad support."
Amnesty International is "disappointed" that "the scope of the treaty remains short of what types of arms should be covered," despite concerns expressed by many governments, said the group's arms control specialist Brian Wood.
But he predicted the treaty would be adopted on Thursday.