He made the comments after a meeting with new EU diplomacy chief Kaja Kallas and EU Council chief Antonio Costa, who visited Kiev in a show of support on their first day of work.
"Inviting Ukraine to join NATO is a necessary thing for our survival," Zelensky said at a news conference with Costa.
Ukraine faces a tough winter as Russia unleashes devastating barrages against its energy grid and Kiev's weary forces lose ground on the front line.
Questions are also swirling about future US support once Donald Trump takes office in January, with fears that he could force Kiev to make painful concessions in his quest for a quick peace deal.
Zelensky said his country needed to be in a "strong position" ahead of any talks with the Kremlin, calling for "steps forward with NATO" and a "good number" of long-range weapons to defend itself.
"Only when we have all these elements and we are strong, then we have to do the very important...agenda of meeting with one or another of the killers," the Ukrainian leader said, adding that the EU and NATO should be involved in any negotiations.
Kostya said the European Union would give Ukraine its "unwavering" support.
"We have been with you since the first day of this war of aggression and you can count on us to continue to support you," he told Zelensky .
The European Union's new leadership team is keen to show it remains determined to support Kiev at a dangerous time for Ukraine, which has been fighting the Russian invasion for almost three years.
This week, Russian President Vladimir Putin threatened to hit government buildings in Kiev with his new Oreshnik missile after the US gave Ukraine permission to fire long-range ATAMS missiles at Russian territory for the first time.
On 1 December, Russian drones dropped explosives on a bus in the southern Kherson region, killing three people, authorities said, and the Russian army said it had captured 2 new villages on the front line in the east of the country.
On 29 November, Zelensky appeared to have begun defining his position ahead of possible peace talks.
He called on NATO to offer guaranteed protection to the parts of Ukraine controlled by Kiev to "stop the hot phase of the war," and hinted that he would then be willing to wait to retake other territories seized by Russia.
"If we are going to have a frozen conflict without any strong position on Ukraine, Putin will come back in two, three or five years," Zelensky said.
During his trip to Ukraine, Kallas told reporters that for Kiev, "the strongest guarantee of security is NATO membership."
"We definitely need to discuss this - if Ukraine decides to draw the line somewhere, then how can we guarantee peace so that Putin doesn't go any further," she said.
NATO diplomats, however, say there is no prospect of the alliance granting Ukraine membership any time soon, as a number of members oppose it for fear of being drawn into a war with Russia.
Zelensky insists Kiev is "not deluded" about its NATO prospects and acknowledges there is deep reluctance from US President Joe Biden as well as leaders of countries such as Hungary. | BGNES
