Volodymyr Zelensky said that Ukraine needs more time to launch a large-scale counter-offensive after one of his units said they had driven a Russian brigade away from Bakhmut.
The Ukraine president said the military is still awaiting the delivery of promised aid despite troops, some of which were trained by NATO countries, being “ready”.
Speaking at the presidential palace in Kyiv, President Zelensky said: “With [what we already have] we can go forward, and, I think, be successful.
“But we’d lose a lot of people. I think that’s unacceptable. So we need to wait. We still need a bit more time.”
The long-anticipated counter attack will be a crucial test for Ukraine forces eager to prove weapons received from the West can make a decisive difference in the 15-month war.
The interview was reportedly carried out in Kyiv with public service broadcasters who are members of Eurovision News, including the BBC.
"So we need to wait. We still need a bit more time," Zelensky was quoted as saying.
A Ukrainian fightback against Russia's invasion has been expected for weeks. Ukraine is receiving advanced Western weapons, including tanks and air defenses, and Western training for its troops as it gears up for an expected assault.
The Kremlin's forces are deeply entrenched in eastern areas of Ukraine with layered defensive lines reportedly up to 20 kilometers (12 miles) deep. Kyiv's counteroffensive would likely face minefields, anti-tank ditches and other obstacles.
Russian President Vladimir Putin is counting on reducing the war to a so-called frozen conflict, with neither side able to dislodge the other, Zelensky said, according to the BBC. He ruled out surrendering territory to Russia in return for a peace deal.
Military analysts have warned that Putin is hoping that the West's costly support for Kyiv will begin to fray.
Ukraine's Western allies have sent the country 65 billion euros ($70 billion) in military aid to help thwart the Kremlin's ambitions, and with no peace negotiations on the horizon the alliance is gearing up to send more.
A senior NATO official said that in the coming months of the war, Ukraine will have the edge in quality but Russia has the upper hand in quantity.
"The Russians are now starting to use very old materiel, very old capabilities," Adm. Bob Bauer, chair of the NATO Military Committee, told reporters late Wednesday in Brussels.
"The Russians will have to focus on quantity," he said. "Larger number of conscripts and mobilized people. Not well-trained. Older materiel, but large numbers, and not as precise, not as good as the newer ones."
Over the winter, the conflict became bogged down in a war of attrition with both sides relying heavily on bombardment of each other's positions.
A counteroffensive is a major challenge, requiring the Ukrainian military to orchestrate a wide range of capabilities, including providing ammunition, food, medical supplies and spare parts, strung along potentially extended supply lines.
The front line extends more than 1,000 kilometers (600 miles).
The Kremlin wants Kyiv to acknowledge Russia's sovereignty over Crimea and also recognize September's annexation of the Ukrainian provinces of Donetsk, Kherson, Luhansk, and Zaporizhzhia.
Ukraine has rejected the demands and ruled out any talks with Russia until its troops pull back from all occupied territories.
