NATO Secretary-General Mark Rutte said he considered the sometimes harsh criticism of German Chancellor Olaf Scholz by Ukrainian President Volodymyr Zelenskyy to be unjustified, news wire DPA reported.

Although Germany has been a vital ally of Ukraine, its hesitation in providing long-range Taurus cruise missiles has been a source of frustration in Kyiv, which is battling a foe armed with a powerful array of long-range weaponry.

"I have often told Zelenskyy that he should stop criticizing Olaf Scholz, because I think it is unfair," DPA quoted Rutte on Monday as saying in an interview.

Rutte also said that he, unlike Scholz, would supply Ukraine with Taurus cruise missiles and would not set limits on their use.

"In general, we know that such capabilities are very important for Ukraine," Rutte said, adding that it was not up to him to decide what allies should deliver.

After a November telephone call by Scholz with Russia's leader Vladimir Putin in November, Zelenskyy said it had opened a Pandora's box that undermined efforts to isolate the Russian leader and end the war in Ukraine with a "fair peace."