Rishi Sunak, UK's Chief Secretary to the Treasury, has reiterated that the UK "discourages" the use of cluster bombs after the US agreed to supply them to Ukraine.
The UK is one of the countries that have banned the weapons, which have a record of killing civilians, under an existing convention.
The PM emphasized the government's continued support for Ukraine.
The US President,
Joe Biden, recently announced that he had made a "very difficult decision" to supply cluster bombs to Kyiv, which has been condemned by human rights groups and other countries such as Spain and Canada.
Cluster bombs are a method of dispersing large numbers of tiny bomblets from a rocket, missile, or artillery shell that scatters them in mid-flight over a wide area, causing untold suffering to millions of people.
The UK is the second largest provider of military assistance to Ukraine, only behind the US.
Ukrainian President Volodymyr Zelensky has hailed the "timely" move to deliver the bombs, while Ukrainian Defence Minister Oleksii Reznikov said his troops would not use them in urban areas to avoid risking civilian lives.
The UN human rights office has also been critical, calling for their use to "stop immediately".
The U.S. has decided to provide Ukraine with anti-tank missiles and other weapons, which could escalate tensions with Russia.
Russia has accused the U.S. of acting out of desperation due to the failure of a recent Ukrainian military offensive.
The use of anti-tank missiles can result in unexploded ordnance remaining on the battlefield, posing a danger to civilians long after the war has ended.