Campaigners are hailing the treaty as a major breakthrough.

More than 100 countries are expected to sign, but some of the biggest stockpilers, including the US, Russia and China will not be among them.

First developed during World War II, cluster bombs contain a number of smaller bomblets designed to cover a large area and deter an advancing army.

But campaigners, including some in the military, have long argued they are outmoded and immoral because of the dangers posed to civilians from bombs that do not explode and litter the ground like landmines.