A Ukrainian MP has said it would be difficult for her country to give up on ambitions to join NATO as Moscow and Kyiv continue talks over an end to war.
Lesia Vasylenko said joining the alliance was "a course that we have decided to take and proscribed it specifically in our constitution".
Meanwhile, the Kremlin said negotiators were discussing a status for Ukraine similar to that of Austria or Sweden, both members of the European Union that are outside the NATO military alliance.
Ukraine's chief negotiator said Kyiv was still demanding a ceasefire and the withdrawal of Russian troops, with guarantees.
But Zelensky has said Ukraine could accept international security guarantees that stopped short of its longstanding aim to join NATO.
Want all the latest news and analysis from Ukraine? Sign up to our World News Bulletin here
That prospect has been one of Russia's primary concerns.
"Neutral status is now being seriously discussed along, of course, with security guarantees," Russian Foreign Minister Sergey Lavrov said. "There are absolutely specific formulations which in my view are close to agreement."
Vladimir Medinsky, Russia's chief negotiator, told state TV: "Ukraine is offering an Austrian or Swedish version of a neutral demilitarised state, but at the same time a state with its own army and navy."
Kremlin spokesman Dmitry Peskov said the idea "could really be seen as a compromise".
Austria and Sweden, the biggest of six EU members outside NATO, both have small militaries that cooperate with the alliance.
Yet Vasylenko, a member of Ukraine's Holos party, told ITV's Peston programme: "Joining Nato for Ukraine, it's a course that we have decided to take and proscribed it specifically in our constitution.
"So it would be very difficult to give that course up, that would mean changes to the constitution.
"Today, as the escalation of Russia's aggression grows against Ukraine, the support for Nato grows with it."
Earlier, UK Prime Minister Boris Johnson said: "We've made it clear to Putin that there is no way Ukraine is going to join NATO any time soon."
Addressing Johnson and representatives from Baltic and northern European countries gathered on Tuesday in London, Zelensky expressed his frustration that Ukraine had not been allowed to join NATO, but said: "This is the truth and we have simply to accept it as it is."
But asked about the comments as well as the prospect of dropping the demand in order to agree a ceasefire, Ms Vasylenko said: "I actually think that was taken out of context by many of the Western media.
"What President Zelensky actually said today during his speech in Congress and during the many meetings that he was having is that Ukraine calls for a coalition of responsible leaders of the free world, and that coalition, he called it the 'U24.'
"Basically the Ukraine 24, of the countries who would be prepared to stand up to Putin and free the world, and Ukraine, from Putin's aggression in 24 hours."
She said she did not trust the Russian negotiators to keep their side of the deal in any agreement.
The Financial Times reported that a draft proposal for a peace plan included promises for Ukraine not to seek to join NATO or to host foreign military bases.
Zelensky, since addressing the London summit, has suggested peace talks between the Ukrainian and Russian delegations had started to produce hope of a ceasefire.
In his nightly video address to the nation early on Wednesday, the president said Russia's demands were becoming "more realistic".
Johnson said decisions about the future of the country had to "be for the Ukrainian people" and their "elected leader" to make, as he vowed Britain would continue to "back" Zelensky.
