Iran and North Korea blocked agreement Thursday on the first treaty over the $80 billion a year conventional arms trade, forcing last-ditch talks to save the UN-brokered accord.
Diplomats from the two isolated states raised flags of objection on the last day of the final session of the seven-year-old negotiating process, just as the conference chairman was about to declare the treaty sealed.
Syria also protested over the final treaty text but said it would not block the accord, which has been at the center of intense diplomatic efforts to get the United States, Russia, China and other major arms producers to agree.
The draft treaty would cover tanks, armored combat vehicles, large-caliber artillery systems, combat aircraft, attack helicopters, warships, missiles and missile launchers, as well as small arms and light arms.
The UN estimates that 500,000 people are killed in armed violence each year and rights groups blame the uncontrolled flow of weapons for many of the deaths.
Iran and North Korea said there were too many restrictions, however.
"The inherent right of states to self-defense, to defend against aggression and preserve its territorial integrity is not addressed," Iran's UN Ambassador Mohammad Khazaee told the conference.
A North Korean diplomat said the proposed treaty was a "risky draft which can be politically manipulated by major arms exporters." He also complained that it undermined the rights of arms importers.
Conference chairman Peter Woolcott of Australia had been just about to bring the gavel down to announce the accord when the two states acted. Woolcott suspended the meeting for behind-the-scenes talks.
If there is no accord by 0400 GMT on Friday, the whole negotiations will collapse. A previous attempt to agree on an accord in July also ended in failure and the UN General Assembly ruled that this would be the last attempt.
But supporters of the treaty could seek a vote next week in the full General Assembly. A two-thirds majority of the 193 members would be required for adoption.
The treaty, if passed, would be the most important weapons accord since the 1996 Comprehensive Nuclear Test Ban Treaty.
The UN General Assembly passed a vote in 2006 calling for a treaty on the unregulated trade in conventional weapons.
The draft negotiated since would aim to force countries to assess whether the sale of a weapon could be used for genocide, war crimes or by terrorists or organized crime gangs.
Woolcott handed out what he called a "take it or leave it" text to UN states on Wednesday and gave them 24 hours to consider their response.
Diplomats said they did not expect the major arms producers to block the treaty.
The United States opposes ammunition coming under the full controls imposed by the treaty. Ammunition has, however, been left in an annex that does not impose compulsory monitoring of trade in bullets, for which the United States is the biggest producer.
Some diplomats said Russia could still refuse to sign the accord, which could weaken its application.
"Moscow believes the text is not strong enough on arms trafficking and that it should explicitly mention 'non-state actors,'" such as the Syrian and Chechen rebels, said one European negotiator.
China and Russia also had concerns about the reporting of arms sales.
The latest text says that "reports may exclude commercially sensitive or national security information."