More than 120 countries are meeting in New Zealand to discuss an agreement limiting the use of cluster bombs.
Unexploded bomblets may pose a hazard to civilians
The talks - launched last year - aim to smooth progress towards the signing of a global treaty later this year.
But some major producers and buyers of cluster bombs - including the US, Israel, Russia and China - are absent.
Cluster bombs are controversial because they often fail to explode on contact with the ground, and may later end up killing or maiming civilians.
The UN has estimated that 40% of the victims of cluster bombs are children.
As well as government representatives from 120 countries, campaigners and survivors of cluster bombs are attending the talks in the capital, Wellington.
The talks seek to reach agreement on exactly which weapons should be banned under the proposed convention.
Under the proposed agreement, countries which use the weapons would also be responsible for disposing of them at the end of hostilities.
"What we're trying to prohibit is those cluster munitions that cause unacceptable harm to civilians," the conference chairman, New Zealand disarmament ambassador Don Mackay, told the Associated Press news agency.
Some 41 of 76 nations which are major holders of cluster bomb stocks are reported to be attending the talks.
Despite the absence of some major producers, reaching an agreement in Wellington would be a "pivotal" step in the process of eventually establishing a meaningful accord, said the minister for disarmament and arms control, Phil Goff.
It is estimated that between 10% and 40% of the bomblets released by cluster bombs just above the ground fail to detonate, posing a threat to civilians in the area.
Some opponents of an outright ban suggest instead the development of "smart" cluster munitions, that can be better targeted and that do not leave behind many unexploded bombs.
Final diplomatic negotiations on the proposed convention are scheduled for May in Ireland.