He specifically singled out Ukraine's need for artillery shells and air defence systems.

"Our partners have all of these things and they should be working now here in Ukraine destroying the Russian terrorist ambitions.

"Russia's army is preparing for further offensive actions," said Mr Zelensky.

Mr Stoltenberg agreed that Kyiv needed weapons, saying that "Ukraine has been outgunned for months, forced to ration its ammunition".

The Nato chief said the six-month delay in US military aid had resulted in "serious consequences on the battlefield".

But Mr Stoltenberg added that he was optimistic that when the arms were delivered it would help turn the tide.

"Our allies are looking into what more they can do and I expect new announcements soon. So we are working hard to meet Ukraine's urgent needs," said the Nato chief.

Mr Stoltenberg also stressed that Ukraine would one day become a Nato member - a key strategic goal for Kyiv; but added that an official invitation at the alliance's Washington summit in July was unlikely.

Russia said it had captured the village of Semenivka, which lies north of Avdiivka which Moscow took in February . On Sunday, Russia said the nearby village of Novobakhmutivka had fallen to its forces.

Ukraine's commander-in-chief Oleksandr Syrskyi has said the situation on the frontline has worsened in the face of multiple Russian attacks, and that Ukrainian forces had withdrawn from positions in the eastern Donetsk region.