Russia’s defence minister said on Tuesday that Western arms supplies to Ukraine were effectively dragging NATO into the conflict, warning this could lead to an “unpredictable” escalation.

“The U.S. and its allies are trying to prolong the conflict as much as possible,” Defence Minister Sergei Shoigu said in a conference call with military officials.

“To do this, they have started supplying heavy offensive weapons, openly urging Ukraine to seize our territories. In fact, such steps are dragging NATO countries into the conflict and could lead to an unpredictable level of escalation.”

His allusion to “our territories” appeared to be a reference to four regions in eastern and southern Ukraine – Donetsk, Luhansk, Zaporizhzhia and Kherson – that Russia claims to have annexed following referendums last September condemned by Kyiv and its Western allies as illegitimate.

Much of the territory in the Russian-claimed regions remains in Ukrainian hands.

Moscow has repeatedly accused the West and NATO military alliance of playing a direct role in the Ukraine conflict by supplying arms to Kyiv, and has warned that NATO weapons are “legitimate targets” for its armed forces.

The United States has sent more than $20 billion worth of military aid to Ukraine since Russia’s invasion last February, and is set to provide Kyiv with longer-range rockets as part of a new $2 billion package of weapons announced last week.

Ukraine says the weapons as well as other military supplies including tanks are urgently needed to stave off Russian attacks and boost its firepower for a spring offensive against Moscow’s forces. Ukrainian officials say Moscow is accumulating arms and reserves for a renewed assault in the coming weeks.

Shoigu also said on Tuesday that military operations near Vuhledar and the city of Bakhmut in eastern Ukraine – where Russia has intensified its offensive – were “progressing well”.

Fighting has focused for months around the Ukrainian-held city of Bakhmut in eastern Donetsk province, which Russia has been trying to encircle.

Moscow has also launched an assault further south against Vuhledar, a Ukrainian-held bastion at the strategic intersection between the eastern and southern front lines.