“The occupiers aren’t abandoning their attempts to score at least some victory by launching a new, large-scale offensive,” Mr Zelenskyy said in his nightly video address to the nation.
He said Ukraine’s western allies had “come to understand our needs better”, and that the country was receiving new shipments of weapons.
The deliveries were coming “now, when Russia is trying to step up its attacks, not in weeks or in a month”, Mr Zelenskyy said.
"The European Union is currently preparing a sixth package of sanctions. We discussed this today with [European Council President] Charles Michel," he said.
"We are working to make it truly painful for the Russian military machine and the Russian state as a whole.
"I emphasise in all negotiations that sanctions are needed not as an end in themselves, but as a practical tool to motivate Russia to seek peace."
Mr Zelenskyy also urged the West to quickly implement a full ban on imports of the Russian oil and oil products.