Live updates: follow the latest news on Russia-Ukraine
In his daily late-night address to the nation, Mr Zelenskyy also said he was thankful for Wednesday’s visit by the presidents of Poland, Estonia, Lithuania and Latvia.
In a phone conversation with US President Joe Biden, Mr Zelenskyy said they discussed the new weapons shipment, even tougher sanctions against Russia and efforts to bring to justice those Russian soldiers who committed war crimes in Ukraine.
He also commented on Russia's military approach, saying: "All this feverish activity of the occupiers testifies first of all to their insecurity.
"To the fact that even with significant stocks of Soviet military equipment and a significant number of soldiers, whom the commanders do not spare at all, the Russian troops doubt their ability to break us, to break Ukraine.
"Well, we do everything to justify their doubts."
Mr Zelenskyy also said work was continuing to clear tens of thousands of unexploded shells, mines and trip wires that were left behind in northern Ukraine by the retreating Russians.
He urged those returning to their homes in those towns to be wary of any unfamiliar object and report it to police.