Russian President Vladimir Putin has warned there is a “serious danger” of NATO being drawn further into the Ukraine war if members of the alliance continue to supply military weaponry to Kyiv.

“NATO, of course, is being drawn into the war in Ukraine, what are we talking here,” Putin said at the St. Petersburg International Economic Forum on Friday.

“The supplies of heavy military weaponry to Ukraine are ongoing, they are now looking into giving Ukraine the jets.”

The comment appeared to be a reference to the F-16 fighter jets some members of the NATO alliance are making plans to supply Ukraine with.

NATO, or the North Atlantic Treaty Organization, was formed in the aftermath of World War II to defend Western nations from the Soviet Union and the alliance contains a mutual defense clause where an attack on any one member is considered an attack on all. While Ukraine is not a member of NATO, some NATO members have been supplying Kyiv with tanks, armored vehicles and other weaponry – prompting threats of retaliation from Russia.

German Leopard 2 tanks, British Challenger 2 tanks and American Bradley and Stryker vehicles are among the Western equipment that has been sent to Ukraine.

In late April, NATO Secretary-General Jens Stoltenberg said that NATO allies and partners had delivered more than 1,500 vehicles and 230 tanks to the country.

During his speech in St. Petersburg, Putin said Russia had destroyed tanks “including Leopards” at the front lines.

“And if they are based abroad, but used in fighting we’ll see how to hit them, and where we can hit those means that are used against us in fighting,” Putin said.

“This is a serious danger of further drawing NATO into this military conflict,” he added.

During his speech to the forum, Putin also suggested Russia’s large number of nuclear weapons would “guarantee” its security – noting that Russia had more such weapons than NATO countries.

Russia has a total stockpile of around 6,250 nuclear warheads as of January 2021, according to the Arms Control Association. The US has more than 5,500 while two other NATO member states, Britain and France, have about 220 and 290 nuclear warheads, respectively.

“Nuclear weapons are created to guarantee our security in the broader sense and the existence of the Russian state,” Putin said.

“But first of all, there is no need and secondly the very fact of talking about it reduces the possibility of the threshold for using these weapons being reduced.”

“Also, we have more weapons like this than the NATO countries. They know it and they keep driving towards negotiation on reduction.”

In February, Putin said he would suspend Russia’s participation in the New START nuclear arms reduction treaty with the United States, imperiling the last remaining pact that regulates the world’s two largest nuclear arsenals. Russia’s Foreign Ministry subsequently said the decision was “reversible.”

The treaty puts limits on the number of deployed intercontinental-range nuclear weapons that both the US and Russia can have. It was last extended in early 2021 for five years.

Under the key nuclear arms control treaty, both the United States and Russia are permitted to conduct inspections of each other’s weapons sites.