ST PETERSBURG, Russia, June 7 (Reuters) - President Vladimir Putin said on Friday Russia had no need to use nuclear weapons to secure victory in Ukraine, the Kremlin's strongest signal to date that Europe's deadliest conflict since World War Two will not escalate into a nuclear war.

Since Putin ordered troops into Ukraine in February 2022, he has said on several occasions that Russia would use such weapons if necessary to defend itself - comments the West says are nuclear sabre-rattling.

Asked at the plenary session of the St Petersburg International Economic Forum by moderator Sergei Karaganov, an influential Russian analyst, if Russia should hold a "nuclear pistol to the temple" of the West over Ukraine, Putin said he did not see the conditions for using such weapons.

"The use is possible in an exceptional case - in the event of a threat to the sovereignty and territorial integrity of the country. I don't think that such a case has come. There is no such need," Putin said.

Moscow considers Crimea - which it seized from Ukraine in 2014 - and four other Ukrainian regions now as integral parts of its own territory, raising the possibility of a nuclear strike if Kyiv appeared poised to retake them.

Ukraine has stepped up drone and missile attacks on Russian targets, including in Crimea, and has vowed to drive all Russian forces from its territory.

Putin said he did not rule out changes to Russia's nuclear doctrine, which sets out the conditions under which such weapons could be used.

He also said that if necessary Russia could test a nuclear weapon, though he saw no need to do so at the present time.

The public debate about nuclear strikes on a stage at Russia's premier economic forum appeared to be a Kremlin attempt to reduce nuclear fears just as the Ukraine war escalates towards what both Russian and U.S. diplomats say is its most dangerous phase yet.

Russia and the United States hold nearly 90% of the world's nuclear weapons.

Photo from Reuters