The Kremlin said Wednesday it had no choice but to continue its military offensive on Ukraine and rejected US President Donald Trump's claim that Russia was a "paper tiger".

After meeting Ukrainian President Volodymyr Zelensky a day earlier, the US leader said Ukraine could win back every inch of its territory from Russia, which he characterised as a "paper tiger" with a failing economy. 

"We are continuing our special military operation to ensure our interests and achieve the goals" set by Putin, Kremlin spokesman Dmitry Peskov said, using Moscow's term for its assault on Ukraine.

"We are doing this for both the present and the future of our country. For many generations to come. Therefore, we have no alternative," he added in a radio interview.