Ukrainian President Volodymyr Zelenskyy has challenged his Russian counterpart, Vladimir Putin, to sign a cease-fire to end fighting as the two sides work toset up a meeting to create a lasting peaceafter more than three years of war sparked by Moscow's full-scale invasion of its neighbor.

Speaking at a briefing in Kyiv on June 4, Zelenskyy said such a meeting could include Turkish President Recep Tayip Erdogan and US President Donald Trump as two recent rounds of talks with lower-level delegations failed to make a breakthrough to put a halt to the war.

"We are ready for exchanges but to continue diplomatic meetings in Istanbul at a level that does not solve anything further, I think, is pointless," Zelenskyy said.

"My proposal, which I believe our partners can support, is that we propose to Russians a cease-fire until the leaders meet.... We are ready for such a meeting any day," he added.

Zelenskyy's call for a meeting comes after talks on June 2 in Istanbul -- only the second round of face-to-face negotiations between the two sides in more than three years -- that failed to move the process forward.

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The delegations exchanged specific proposals for a framework for a peace deal.

Ukraine called for, among other things, an unconditional 30-day cease-fire plus the exchange of all prisoners of war, as well as the return of Ukrainian children whom Kyiv said have been abducted by Russia.

Russia's proposal, meanwhile, called for the international recognition of Crimea, the Ukrainian peninsula Moscow annexed in 2014, as well as the four Ukrainianregions that are partially occupied by Russian forces.

Zelenskyy accused the Kremlin of not being serious about negotiating a peace deal -- a charge many Western countries have also leveled -- saying it was a ploy to keep Washington from implementing a new round of harsh economic sanctions on Russia.

"They did it to demonstrate to the United States that they are trying to be constructive," Zelenskyy said, calling the Russian proposal an "ultimatum."

"Why? To have a delay, which depends on President Trump personally: whether or not to postpone the imposition of sanctions."

Responding to Zelenskyy's comments, Russian Foreign Minister Sergey Lavrov rejected the accusation, saying the process of direct talks was working and had produced results.

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A series of audacious attacks by Ukraine on targets inside Russia or areas of Ukraine controlled by Moscow in recent days have sent shock waves across Russia.

On June 1, Ukrainian forcesstruck dozens of long-range bomber aircraftacross Russia with drones smuggled in wooden shipping crates carried on truck beds into the country and then launched from nearby locations.

The Security Service of Ukraine (SBU) claims that more than40 bomberswere hit in the attack, described as an "absolutely brilliant outcome" by Zelenskyy, who added that the operation had taken more than 18 months to prepare.

Then on June 3, Ukraineclaimed to hit a key bridgethat links Russia and Moscow-occupied Crimea with underwater explosives.

Lavrov said Moscow shouldn't fall for Ukraine's "criminal provocations," and instead use negotiations and all "means" it has to achieve its goals in Ukraine.

The 19-kilometer Kerch Bridge, which carries both road and rail traffic, was built by Russia and opened in 2018 -- four years after Moscow illegally annexed the peninsula -- and serves as an important supply route for Russian forces occupying parts of southern Ukraine.

It was damaged by Ukrainian attacks in October 2022 and July 2023 and has frequently been closed during security incidents.