Ukraine's Foreign Minister Dmytro Kuleba accused Germany on Tuesday of ignoring Kyiv's pleas for Leopard tanks and Marder infantry-fighting vehicles, saying Berlin offered only "abstract fears and excuses" for not providing such military hardware.

His comment came after President Volodymyr Zelenskyy made a new appeal to the West to speed up deliveries of weapons systems as Ukrainian forces move to consolidate control over a large swath of northeastern territory recaptured from Russia.

"Disappointing signals from Germany while Ukraine needs Leopards and Marders now — to liberate people and save them from genocide," Kuleba tweeted.

"Not a single rational argument on why these weapons cannot be supplied, only abstract fears and excuses. What is Berlin afraid of that Kyiv is not?," he wrote, in unusually blunt language.

Germany has sent self-propelled howitzers to Ukraine but Zelenskyy and Kuleba say that is not sufficient. Kuleba has often criticized what he says is Germany's slowness in sending weapons, suggesting it is reluctant to antagonize Russian President Vladimir Putin.

One of Zelenskyy's advisers, Mykhailo Podolyak, also took a swipe at Germany.

"For six months the allies have been arguing over who will sell tanks to Ukraine. There are no tanks for six months because there is no 'political solution'. Russia continues its terror, people die, time is wasted. Germany, we are waiting for your word," he said on Twitter on Tuesday.

In talks with Kuleba in Berlin at the weekend, German Foreign Minister Annalena Baerbock promised further military aid and did not rule out the delivery of Western-style main battle tanks, adding the "next few weeks and months will be crucial" for Ukraine.