Russia on Friday ruled out an immediate meeting with Volodymyr Zelensky, as diplomatic tension with the Ukrainian president escalated and US mediation efforts appeared to stall.

Russian Foreign Minister Sergei Lavrov said "no meeting" between Vladimir Putin and Zelensky was planned, as Nato chief Mark Rutte visited Kyiv, largely to discuss security guarantees for Ukraine.

US President Donald Trump had raised expectations for a swift summit between the Russian and Ukrainian presidents by saying earlier in the week they had agreed to meet, but on Friday compared the two men to "oil and vinegar".

"They don't get along too well, for obvious reasons," he told reporters in Washington.

Lavrov also poured cold water on hopes for direct Putin-Zelensky talks to resolve the conflict, now in its fourth year, by questioning the Ukrainian president's legitimacy and repeating the Kremlin's maximalist claims.

"There is no meeting planned," Lavrov said in an interview with NBC's "Meet the Press with Kristen Welker".

Lavrov told the US broadcaster Putin was "ready to meet Zelensky" as soon as an agenda was prepared, adding that the agenda was "not ready at all".

In Kyiv, speaking alongside Rutte, Zelensky said Ukraine had "no agreements with the Russians", saying Ukraine had agreed only with Trump on how the diplomatic direction could proceed.

On Thursday, he had accused Russia of "trying to wriggle out of holding a meeting", adding that Moscow wanted to continue the offensive. (AFP)