Vladimir Putin said on Friday that Russia has delivered tactical nuclear warheads to neighbouring Belarus and warned that his country could use similar weapons in Ukraine, though he said there was “no need” to do so more than a year into his full-scale invasion.

The transfer, if confirmed, would be the first time Russia has deployed nuclear weapons outside its borders since the collapse of the Soviet Union. Russia will retain control over the tactical nuclear arms, which are to be kept in refurbished Soviet-era storage facilities.

Speaking at his flagship economic conference in St Petersburg on Friday, The Russian president said Moscow had sent an unspecified number of nuclear warheads to Belarus, adding that the supplies would be “completely finished by the end of the summer or the end of the year”.

Tactical nuclear weapons, known as “suitcase nukes”, are smaller than strategic ones and can be deployed at short range for battlefield use — though Alexander Lukashenko, Belarus’ strongman leader, said this week that the warheads were three times more powerful than the atomic bombs the US dropped on Japan during second world war.

Putin has said Russia has the right to deploy the weapons because of the number of nuclear armaments the US has deployed in Europe. He has regularly floated the possibility of using them if Russia’s “statehood is threatened” in Ukraine.

Neither Russia nor Belarus have shown any evidence of the nuclear weapons being delivered since they first announced the plan in March.

Though Putin has repeatedly said that Russia is not planning to use a nuclear weapon, he has made increasing reference to the possibility of using them in recent weeks as his invasion of Ukraine continues to sputter.

He had previously raised the topic last autumn, around the time that the US, UK and France warned Russia that they would retaliate with a conventional strike if Putin used nuclear weapons in Ukraine. China, Moscow’s ally, has also repeatedly said the use of nuclear arms would be unacceptable.

Putin told the forum’s audience, made up of Russia’s elite and a smattering of guests mostly from the Middle East, Africa, and Asia, that he would resist any efforts at arms control talks with the west.

“We have more of those weapons than Nato countries. They know that and are always trying to get us to start reduction talks. Screw them, you know, as people say,” Putin said. “Because in this case, to use an economic term, it’s our competitive advantage.”

Putin’s declaration was the centrepiece of a resentful three-hour session in which he repeated, without evidence, claims that Ukraine’s counteroffensive against his invading forces had failed.

He said supplies of advanced western weapons such as Bradley infantry fighting vehicles and Leopard tanks had not given Kyiv the upper hand on the battlefield, and vowed to destroy F-16 fighter jets once Ukraine received them from western allies.

“Tanks are burning, Leopards are among those being destroyed . . . and there is no doubt that F-16s will burn too,” Putin said.

If Ukraine deploys the F-16s outside its own borders but uses them in the counteroffensive, Russia would “look at where and how we can hit the units that are being used in combat operations against us”, Putin said, adding that this raised “the serious risk of Nato being dragged into this armed conflict”.

Putin also claimed that Russia had destroyed five US-made Patriot missile defence units in Kyiv — even though Ukraine and its western allies say it has only been supplied with two, plus additional launchers.

“If we destroy five Patriot systems near Kyiv, what’s to stop us destroying any building or piece of infrastructure in central Kyiv? There are no such limitations,” he said. “We can do that, but we are not doing it for several reasons. There is no need [for this], that’s the first reason. Because the enemy is not successful on the frontline,” Putin added.

He insisted that Russia was justified in starting the war because Ukraine was run by “Nazis”, even though its president, Volodymyr Zelenskyy, is Jewish.

“I have a lot of Jewish friends, since childhood. They say Zelenskyy isn’t a Jew. He is a disgrace to the Jewish people,” Putin said, prompting a round of applause from the audience.

He then broke off his speech to show a short documentary film about the Holocaust in Ukraine during the second world war as his officials and oligarchs looked on.