Ukraine welcomed the US decision to provide cluster munitions, with Defense Minister Oleksii Reznikov outlining “five key principles” that he said would govern the use of the controversial weapons.

Cluster bombs, whose use is banned in over 100 countries including several NATO members and key allies of Ukraine, will be used as the war-torn country presses its counteroffensive against Russia, the Ukrainian said in a lengthy Twitter post.

The weapons will help Ukraine liberate the occupied territories and save the lives of its soldiers, Reznikov said, adding that Article 51 of the UN Charter allows Kyiv to use them as “self-defense.”

“We have five key principles which we will abide by and which we have clearly communicated to all our partners, including the US,” Reznikov said.

These include the obligation not to use the weapons on the officially recognized territory of Russia and in urban areas where they could cause the most harm to civilians.

Fired from aircraft or from ground-based artillery, missile or rocket launchers, cluster munitions open in flight, dispersing bomblets that can strike armored vehicles or personnel and are particularly effective against dug-in forces. Those that fail to explode pose a danger for years, even decades, to civilians.

Ukraine will keep a strict record of use of the weapons and will prioritize de-mining on territories where the bombs are launched “after the victory,” according to Reznikov.

“We will report to our partners about the apply and efficiency of weapons to ensure control,” he said.

Read more: US Sends Cluster Bombs to Ukraine Despite Civilian Threat

Russia condemned the US decision, taken by President Joe Biden months after a request for the weapons was first made by Ukraine.

The move was “another blatant manifestation of the aggressive anti-Russian course of the US” aimed at dragging out conflict in Ukraine,” Russian foreign ministry spokeswoman Maria Zakharova said in a statement.

“Experience of using of cluster munitions in the Middle East and other regions of the world shows that their elements can remain unexploded for a long time and detonate after the end of hostilities,” Zakharova said.

The US, Russia and Ukraine are among the countries that aren’t signatories to the Convention on Cluster Munitions, an international treaty from 2010 that aims to prohibit all use, transfer, production and stockpiling of the weapons.

The UK is one of the 123 signatories. Prime Minister Rishi Sunak said the UK is committed to the convention but added that the UK would continue to support Ukraine, the BBC reported. The defense minister of Spain, another signatory, said the weapons shouldn’t be sent.

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On Saturday, the 500th day of Russia’s invasion, Reznikov said Kremlin forces had been using cluster munitions “from day one.”

In February-March of 2022, Kharkiv, Ukraine’s second-largest city, “was relentlessly bombarded by Russian cluster munitions,” he said.

“Our position is simple - we need to liberate our temporarily occupied territories and save the lives of our people, thus we need to inflict losses on the enemy.”

Read more: Biden Set to Send Cluster Munitions to Ukraine Despite Concern