In a late night speech, the Ukrainian President thanked Europe for applying sanctions, which he said had had a “powerful” impact on Russia.
He said: “You have applied sanctions. We are grateful. These are powerful steps.”
But he added earlier sanctions may have stopped the war, adding: “It was a little late, there was a chance.”
He claimed that blocking the Nord Stream 2 gas pipeline at an earlier stage, would’ve stopped the gas crisis in the continent. Mr Zelensky then called on the EU to not delay Ukraine’s request to join the bloc.
Nato has confirmed it will be sending 40,000 troops in total to Slovakia, Hungary, Bulgaria and Romania.
Ukraine has been pleading with western allies for more weapons, with Mr Zelensky asking Nato for 1 per cent of the organisation’s tanks and jets.
On Thursday he told the alliance: “We will see who is our friend, who is our partner and who has sold us out and betrayed us.”
According to CNN, Ukraine has reportedly told the US it requires 500 Javelin and Stinger missiles a day in order to drive back Russian forces.
Ukraine has also asked the US for hundreds more anti-aircraft and anti-tank missiles, as well as more helicopters, planes and anti-aircraft systems.
It comes as the United Nations (UN) reported that Ukrainian civilians have been held hostage in Russian-occupied regions.
According to the UN’s latest figures, 1,035 civilians have been killed, while a further 1,650 have been injured as of March 24.
There are fears Russia may use chemical weapons in Ukraine as its offensive continues to stall.
The World Health Organisation says it has been unable to send medical supplies to besieged cities Mariupol and Mykolaiv.
US President, Joe Biden, travelled to Europe for a series of summits on Thursday, and said Nato would respond if Vladimir Putin used chemical weapons.
He said: “We would respond if he uses it. The nature of the response would depend on the nature of the use.”
After weeks of fighting, the Ministry of Defence has said Ukrainian forces have reoccupied towns 21 miles east of Kyiv.
In its latest intelligence update, posted on Twitter, the MoD said: “Ukrainian counter-attacks, and Russian forces falling back on overextended supply lines, has allowed Ukraine to reoccupy towns and defensive positions up to 35 kilometres east of Kyiv.
“Ukrainian forces are likely to continue to attempt to push Russian forces back along the north-western axis from Kyiv towards Hostomel Airfield.
“In the south of Ukraine, Russian forces are still attempting to circumvent Mykolaiv as they look to drive west towards Odesa, with their progress being slowed by logistic issues and Ukrainian resistance.”