3D printed natural gas pipes are pictured on EU and Russian flags in this illustration. Reuters
The speech came as Ukrainian President Volodymyr Zelensky reported "good news" from the front near Kharkiv in the east, saying some settlements had been recaptured as both sides reported heavy fighting in the region.
Ukrainian and pro-Russian officials said there was fighting around the town of Balakleiia about 60km (38 miles) southeast of Kharkiv, with unconfirmed reports of heavy losses to Russian forces.
Ukrainian President Volodymyr Zelensky (rights) visits the frontline positions of the Ukrainian military. AFP
An explosion at a power plant near Odesa in the south, meanwhile, cut electricity supplies to 360,000 people, a spokesperson for the regional administration said.
Putin said in a speech on Wednesday to an economic forum in Russia's Far East that Russia would not lose what he calls its "special military operation" in Ukraine.
He threatened to halt all supplies of energy to Europe if Brussels went ahead with its proposed price cap on Russian gas, the latest Western step to deprive the Kremlin of funds to finance the war.
"We will not supply gas, oil, coal, heating oil â€” we will not supply anything" if that occurs, he said. Europe usually imports about 40% of its gas and 30% of its oil from Russia.
Russian President Vladimir Putin speaks during an interview. File photo
The United States and France says Moscow is already using energy as a "weapon" to weaken Europe's opposition to its invasion, with the main conduit for Russian gas into Europe, Nord Stream 1, shut for maintenance.
Ukraine remained guarded about its counter-offensive in the east but presidential adviser Oleksiy Arestovych, in a video posted on YouTube, said Ukrainian troops had surprised Russian defenders at Balakleiia.
"The Russians are saying that Balakleiia is encircled when in fact (our troops) have gone much further ... they've cut off the road to Kupiansk," he said, referring to the main transport hub supplying Russian forces in Izyum to the east.