"We just got them, we haven't used them yet, but they can completely change the battlefield," Ukrainian military commander Oleksandr Tarnavskyi told US television station CNN in an interview.

The US said last week it would supply cluster bombs to Ukraine, despite concerns about the long-term risks to civilians.

Mr Tarnavskyi said that Ukrainian forces would not deploy weapons in densely populated areas.

US President Joe Biden said the decision was “very difficult” but stressed Ukraine needed more ammunition to replenish depleted stocks.

These controversial weapons can disperse hundreds of small munitions and explosives, which may remain unexploded underground, posing a risk to civilians long after a conflict ends.

They are banned by many countries – especially in Europe – who are signatories to the 2008 Oslo Convention, but neither Russia, the US nor Ukraine are party.

Russia has said it will take "retaliatory measures" if Ukraine deploys the weapon against its troops on the battlefield.

Hoang Anh (according to AFP, AP)