Russian President Vladimir Putin's chief spokesman has conceded that Russia has yet to achieve any of its military goals in Ukraine and refused to deny that Moscow could resort to the use of nuclear weapons.

In an interview with CNN's Christiane Amanpour on Tuesday, Dmitry Peskov repeatedly refused to rule out that Russia would consider using nuclear weapons against what Moscow saw as an "existential threat." When asked under what conditions Putin would use Russia's nuclear capability, Peskov replied, "If it is an existential threat for our country, then it can be."

Putin has previously hinted at using nuclear weapons against nations that he saw as a threat to Russia. Back in February, the Russian President said in a televised statement, "No matter who tries to stand in our way or all the more so create threats for our country and our people, they must know that Russia will respond immediately, and the consequences will be such as you have never seen in your entire history."

He then said in a televised meeting with Russian defense officials that "officials in leading NATO countries have allowed themselves to make aggressive comments about our country, therefore I hereby order the Minister of Defense and the chief of the General Staff to place the Russian Army Deterrence Force on combat alert."

When asked what Putin thought he had achieved in Ukraine so far, Peskov answered: "Well, first of all, not yet. He hasn't achieved yet."

The spokesman also claimed that the "special military operation" -- the Kremlin's official euphemism for Russia's invasion in Ukraine -- was "going on strictly in accordance with the plans and the purposes that were established beforehand."

Peskov also repeated Putin's demands, saying that the "main goals of the operation" are to "get rid of the military potential of Ukraine," to ensure Ukraine is a "neutral country," to get rid of "nationalist battalions," for Ukraine to accept that Crimea -- annexed by Russia in 2014 -- is part of Russia and to accept that the breakaway statelets of Luhansk and Donetsk "are already independent states."

He also claimed that Russia has only attacked military targets, despite numerous reports of Russian airstrikes against civilian targets sheltering ordinary Ukrainians.

The interview comes as Western intelligence has reported that Russia's operations have stalled in parts of Ukraine. (CNN)

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