Putin, wearing military uniform and speaking during a visit to a command post on Friday, said the operation was in response to Ukraine's 2024-25 incursion into Russia's western Kursk region.
"The Russian armed forces were tasked not only with expelling the enemy from our land but also with establishing a security zone in the adjacent territory. This task is being carried out successfully," he said in televised comments.
"Our goal is to ensure the absolute security of Russia's border regions for the future, and we do not plan to make this a subject for potential peace negotiations with Ukraine."
Kremlin spokesman Dmitry Peskov said the planned security zone spanned 660km, of which 70 per cent was currently under Russia's control. He did not say how deep it would reach inside Ukraine.
Putin has spoken before about the need for such a zone but has not previously spelt out the planned extent of it or said it would be off-limits for talks.
It requires Russia to carve out land in the Sumy and Kharkiv regions, which are not among those it has claimed as its own territory since launching the war in Ukraine in 2022.
Putin, who rarely dons military uniform, struck a hawkish and confident tone in his comments to senior officers.
He was speaking at a critical point in diplomacy over the war, one week after a deal to sell Russian diesel to the US that has won favour with President Donald Trump and prompted a new souring of the relationship between Trump and Ukrainian leader Volodymyr Zelenskiy.
Putin said Russian forces had yet to capture just over 10 per cent of the territory of Ukraine's Donetsk region, a key objective, and 16.5 per cent of the Zaporizhzhia region.
He praised the effectiveness of Russian strikes against Ukrainian military, industrial and logistics targets, while adding there was still room for improvement in Russia's own air defences.
Ukrainian drones have attacked several Russian data centres and a big oil refinery in the past nine days, while Russia has continued to pound Ukrainian cities, power plants and ports, among other targets.
Earlier, Putin's investment envoy Kirill Dmitriev said Russia and the US were discussing a range of new joint projects including nuclear-powered data centres in the wake of last week's agreement on diesel.
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