Zelenskiy's comments drew an immediate rebuke from Moscow, which said Kyiv's approach to NATO could further inflame the situation in Donbass, where violence has increased in recent days.
The restrained response to Zelinskiy's request by the United States - which has strongly supported Ukraine as it faces the Russian military buildup - suggested a desire to avoid unnecessarily antagonizing the Kremlin any further.
White House press secretary Jen Psaki noted that Ukraine has long aspired to joining NATO and that Washington and Kyiv have been discussing the issue.
State Department spokesman Ned Price restated U.S. policy of supporting an "open door" to NATO for countries meeting "the standard for membership." But Ukraine, he said, still must "implement the ... reforms necessary to build a more stable, democratic, prosperous and free country."
A Pentagon spokesman declined to answer when asked at a briefing to comment on Zelenskiy's request. But hours later, the Pentagon released a statement noting that the alliance in 2018 reaffirmed a decision that Ukraine "will" become a member, adding that any questions on the matter be addressed to NATO.
Russian-backed separatists have fought since 2014 against Ukrainian forces in the Donbass, a conflict that Kyiv says has killed 14,000 people. Kyiv reported two more soldiers killed on Tuesday and, in a separate statement, Zelenskiy said 24 Ukrainian soldiers had been killed since the start of the year.
"NATO is the only way to end the war in Donbass," Zelenskiy told NATO Secretary General Jens Stoltenberg in a phone call, according to a statement from Zelenskiy's office. A Membership Action Plan laying out Ukraine's entry path into the alliance "will be a real signal for Russia", he said.
He also called for NATO members to strengthen their military presence in the Black Sea region.
Stoltenberg in a tweet expressed "serious concern about Russia's military activities in and around Ukraine & ongoing ceasefire violations".
Ukraine has launched a diplomatic offensive to shore up support from Western countries and NATO in its standoff with Russia over Donbass, sounding the alarm since late March over the build-up of Russian troops. Russia says the troop movements are defensive and that NATO involvement would inflame the situation.
The standoff has also pushed Ukrainian sovereign bonds to their lowest level since November.
KREMLIN SAYS RHETORIC COULD INFLAME
Kremlin spokesman Dmitry Peskov said those living in eastern Ukraine would not accept NATO membership, and that rhetoric could further destabilise the Donbass region.
"So far we're not seeing an intention by the Ukrainian side to somehow calm down and move away from belligerent topics," he said.
Foreign Minister Sergei Lavrov, speaking during a visit to India, said Russia was worried by statements coming out of Kyiv, and was in touch with European countries about them.
The Donbass conflict erupted in the months after Russian forces seized Ukraine's Crimean peninsula in 2014. Ukraine and Western countries says Donbass separatists have been armed, led, funded and aided by Russians, including active Russian troops.
Moscow has denied interfering. While a ceasefire halted full-scale warfare in 2015, sporadic deadly fighting never ceased.
Ukraine also said on Tuesday it wanted to move ongoing peace talks away from the Belarusian capital Minsk, saying Belarus was too much under the influence of Russia.
"We don't know where (the talks) could be relocated. This is the subject of discussion," Ukraine's Deputy Prime Minister Oleksiy Reznikov told Reuters.
(Reporting by Pavel Polityuk and Natalia Zinets in Kyiv, Tom Balmforth and Vladimir Soldatkin in Moscow, Gabriela Baczynska in Brussels, Karin Strohecker in London, Phil Stewart, Jonathan Landay and Trevor Hunnicutt in Washington;
Writing by Matthias Williams; Editing by Peter Graff and Jonathan Oatis)
Source: Reuters