The Vatican's Secretary of State, Cardinal Piero Parolin, expressed his concerns regarding the conflict between Ukraine and Russia when speaking to journalists on the margins of a book presentation in Milan this week. He said of the use of NATO weaponry against Russia, “I think it should concern every person that cares about the fate of our world.

"It could lead to an escalation that no one will be able to control, it is a disturbing prospect.”

These comments came as NATO considers letting Ukraine target Russian territory with provided weapons, a move supported by leaders from the UK, France, Germany, and the US.

Discussion on this point has increased in recent days after Russia launched a new offensive in Kharkiv, the latest of its efforts to make advancements in Ukraine after initiating a full-scale invasion in February 2022.

British Foreign Secretary David Cameron in early May said Ukraine could use weapons provided by London on targets inside of Russia, and that it was up to Kyiv to decide whether to do so.

During a 5-day trip to Germany on Tuesday, French President Emmanuel Macron stated, “we should permit the neutralization of military sites launching missiles, and those from which Ukraine is targeted.”

At a joint press conference with Macron, German Chancellor Olaf Scholz endorsed this stance, a view also held by multiple Eastern European NATO members.

On Thursday, United States President Joe Biden eased some limits on the use of military aid provided to Ukraine by the US, signaling a move towards allowing the use of American weaponry on Russian soil.

In response to the West's potential military aid to Ukraine, Russian Senior Security Official Dmitry Medvedev warned of significant consequences. In a statement he said: “This is no military assistance, this is participation in a war against us,” adding that such actions could well become a "casus belli," or an act provoking war.