BBC
Britain is to take cluster bombs out of service, Prime Minister Gordon Brown has said.
The announcement came as diplomats in Dublin were said to be "very close" to reaching an international treaty banning their use.
Mr Brown called it a "big step forward to make the world a safer place" and said he hoped more states would follow.
But some of the world's main producers and stockpilers - including the US, Russia and China - oppose the move.
A final draft of the new convention banning cluster bombs was expected to go before delegates on Wednesday afternoon.
The British Foreign and Commonwealth Office (FCO) said negotiations could result in a deal by the end of the week, possibly sooner.
'Bomblets'
Cluster bombs have been used in countries including Cambodia, Kosovo, Afghanistan and Lebanon.
They are made up of a big container which opens in mid-air, dropping hundreds of smaller individual bombs, or sub-munitions, across a wide area.
These "bomblets" usually explode once they hit their target, but can fail to do so, leaving a deadly legacy as civilians return to their homes.
See how a cluster bomb works
In a statement, Mr Brown said: "After 10 days of intense talks in Dublin, we are now very close to agreement on a new international convention prohibiting the use, production, stockpiling and transfer of cluster munitions that cause unacceptable harm to civilians.
"In order to secure as strong a convention as possible in the last hours of negotiation we have issued instructions that we should support a ban on all cluster bombs, including those currently in service by the UK.
"We will now work to encourage the widest possible international support for the new convention."
Mr Brown said the convention would be a "major breakthrough" in the effort to eliminate cluster bombs.
Simon Conway, from campaign group the Cluster Munition Coalition, said: "I believe this is a personal intervention by Mr Brown on humanitarian grounds.
"It is a major act of statesmanship."
An FCO spokesman told the BBC there were still a number of possible sticking points, including the issue of interoperability.
This involves deciding how to deal with a situation where troops from a country that has signed the treaty are involved in coalition operations with forces from a country that has not.
Another point of contention is the degree of obligation that should be placed on signatories to clear unexploded sub-munitions.
The BBC's Paul Adams said he understood the agreement would effectively outlaw the two cluster munitions currently held by UK forces, but would not prevent countries from developing future generations of weapons based on the concept of sub-munitions.
He said it appeared the UK was seeking a deal which other countries not present in Dublin, notably the US, might be persuaded to accept later.
Using British soil
Another stumbling block could be the stockpile of cluster munitions the US military keeps at bases on British soil.
Our correspondent said the UK did not appear to be pushing for a ban on the practice, but John Duncan, the British representative in Dublin, said the draft treaty would prevent stockpiling after eight years.
The UK would work with Washington to find a solution to the issue, he added.
But Liberal Democrat foreign affairs spokesman Ed Davey said: "If he [Mr Brown] is serious about ending the scourge of these weapons, he must bring this abuse of the 'special relationship' to an end."
The proposed ban has the support of more than 100 countries and many humanitarian organisations.
Jakob Kellenberger, president of the International Committee of the Red Cross, said: "Cluster munitions are weapons that never stop killing."
Pope Benedict XVI has also spoken out in support of a "strong and credible international agreement" to prohibit cluster bombs.
But countries like the US, India, Pakistan and Israel claim such munitions can be highly useful on the battlefield and want to see the treaty watered down.
How will the ban be enforced? Will it even be enforced?
Jakob Kellenberger, president of the International Committee of the Red Cross, said: "Cluster munitions are weapons that never stop killing."
That doesn't make sense, or is it just me. Of course they stop killing, they stop once they've exploded, they don't "never stop killing".