Kremlin spokesman Dmitry Peskov said it was unlikely that such a meeting could occur by the end of August, as Ukraine has proposed.
"A summit meeting can and should put the final point on a settlement and cement the modalities and agreements worked out by experts. It is impossible to do it the other way round," Peskov told reporters.
"Is it possible to go through such a complex process in 30 days? Well, obviously, it is unlikely."
Ukraine says a leaders' meeting is required in order to achieve a breakthrough in the slow-moving process, which has seen the two sides hold three brief sessions of peace talks in Turkey since mid-May.
In comments to journalists, Zelenskiy said Russia had begun to engage over the possibility of such a meeting.
"Now, in talks with us, they have begun to discuss it. This is already progress towards some kind of meeting format," he said.
A Ukrainian delegate said after the latest round of peace talks on Wednesday, which lasted just 40 minutes, that Kyiv had proposed a Putin-Zelenskiy meeting in August because that would fall within the 50-day deadline that US President Donald Trump had set last week for a deal.
Trump has threatened new sanctions on Russia and buyers of its exports unless an agreement is reached by early September.
Peskov once again described the two sides' negotiating positions as "diametrically opposed".
"It is unlikely that they can be brought together overnight. This will require very complex diplomatic work," he said.
Meanwhile Zelenskiy has reversed course on a bill affecting the independence of Ukrainey's anti-corruption agencies in an effort to defuse a public outcry.
Earlier this week he approved a controversial law that was seen as undermining the agencies' autonomy - sparking Ukraine's first major protests since the beginning of the war with Russia, and sharp criticism from the European Union.
Zelenskiy said parliament would review a new bill, which "guarantees real strengthening of Ukraine's law enforcement system, the independence of anti-corruption bodies, and reliable protection of the legal system from any Russian interference."
Ukraine's two main anti-graft agencies - the National Anti-Corruption Bureau of Ukraine and the Specialised Anti-Corruption Prosecutor's Office - quickly welcomed Zelenskiy's new proposal, saying it restores all their procedural powers and guarantees their independence.
The agencies said they helped draft the new bill, and urged lawmakers to adopt it "as soon as possible" to prevent threats to ongoing criminal cases.
Critics said the law approved by Zelenskiy earlier this week stripped Ukraine's anti-corruption agencies of their independence by granting the government more oversight of their work.
The president initially argued the law was needed to speed up investigations, ensure more convictions and remove Russian meddling.
After Thursday's U-turn, Zelenskiy said the new bill reverses the earlier changes and also introduced additional measures aimed at "combating Russian influence," including mandatory polygraph tests for law enforcement officers.
Fighting entrenched corruption is crucial for Ukraine's aspirations to join the EU and maintain access to billions of dollars in Western aid in the war. It is also an effort that enjoys broad public support.
The unrest has come at a difficult time in the all-out war. Russia's bigger army is accelerating its efforts to pierce Ukraine's front-line defences and is escalating its bombardment of Ukrainian cities.
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