BRUSSELS (NYTIMES) - President Volodymyr Zelensky of Ukraine called publicly on Saturday (March 19) for direct negotiations with President Vladimir Putin of Russia, but a senior Turkish official said that Mr Putin was not ready for such talks.

"Zelensky is ready to meet, but Putin thinks that the positions to have this meeting at the leaders' level are not close enough yet," said Mr Ibrahim Kalin, a chief adviser and spokesman for President Recep Tayyip Erdogan of Turkey.

Turkey and Mr Erdogan are playing a significant mediating role between Russia and Ukraine, trying to find a path towards a longer-term cease-fire and serious negotiations on a peaceful resolution to a brutal war that has lasted more than three weeks.

While Turkey is a member of Nato, Mr Erdogan has good relations with Mr Putin, despite the Russian leader's antipathy towards the Western military alliance of 30 nations.

Mr Erdogan spoke to Zelensky and Mr Putin on Thursday to gauge their positions, and Mr Kalin was on the calls.

The Turkish official said that Mr Putin no longer advocated replacing Mr Zelensky but "now accepts the reality of Zelensky as the leader of the Ukrainian people, whether he likes it or not".

"I believe that meeting will take place at some point," Mr Kalin said. "There will be a peace deal at some point. Of course, we all want this to happen sooner rather than later, but probably Putin thinks that he wants to be in a position of strength when he does that, and not appear to be weak, weakened by either military losses or by the economic sanctions."

That time is not yet and may not be soon, Mr Kalin said. But the economic sanctions are probably having the most effect on Mr Putin's thinking, he said.

The Ukrainians "want a peace deal sooner rather than later, regardless of the opinions of others", he said, even if some Nato countries are worried about Russia being rewarded for its war of aggression while at the same time being unwilling to fight the Russians themselves.

But the main difficulty will be how to preserve Ukraine's territorial integrity and sovereignty, which Ukraine and its allies will not sacrifice. That includes the Crimean Peninsula, which Russia annexed eight years ago. Even if Crimea is "de facto Russian," he said, no one will concede to "de jure" annexation.

Ideally, Mr Kalin said, the solution will be found in some new version of the Minsk accords, which were meant to provide significant autonomy within Ukraine to the Russian-supported separatist enclaves of Donetsk and Luhansk.

That is now more complicated since Mr Putin and the Russian Duma, or parliament, have recognised the separatist enclaves as "independent" states covering land not now under their control, as Russia did with South Ossetia and Abkhazia in Georgia after a similar war in 2008.

Russian and Ukrainian officials have been negotiating in Belarus and over video calls. But the Russian delegation is relatively low-level, and so far the talks have not touched on the hardest problems separating the two sides, leading Ukrainian officials to believe that Russia is delaying while its military offensive grinds on.

The most difficult issues, like those of territorial control and sovereignty, will have to be left to the two presidents, Mr Kalin suggested, once lesser issues are resolved. Those include Ukraine agreeing to a form of neutrality barring Nato membership, which Mr Zelensky already appears to concede.

"The Russians are ready to move to another level of negotiations," Mr Kalin said.

But it will also be important for Turkey and its fellow Nato members to start thinking seriously about how to manage relations with Russia once the war ends, Mr Kalin said.

"Even though we fully reject the Russian war on Ukraine, the Russian case must be heard, because after this war, there will have to be a new security architecture established between Russia and the Western bloc," he said.

"We cannot afford another Cold War; it will be bad for everyone and costly for the entire international political and financial system," he said.

"Every decision we make, every step we take now with regards to Russia militarily, politically, economically and otherwise, will have an impact on that new security architecture."

That topic will be part of an extraordinary summit meeting of Nato countries on Thursday, which President Joe Biden plans to attend. While mostly intended as a show of unity in the face of Russian aggression, to emphasise the alliance's commitment to deterrence and collective defence, Mr Kalin said, "at the end of the day, the goal is to establish peace and security for all".

That is why Turkey is trying so hard "to keep our lines of communication open with Russia," he said.

"Of course, Russia bears the greater responsibility here," he said, but "at the end of the day, it's President Putin who will call this war off. When he will feel like doing it, when he thinks that he has gotten what he wanted out of this war - compromise, concession, deal - I do not know. But I think we are moving in that direction."