As diplomacy drags on, peace seems far off in Ukraine.

BRUSSELS — Ukraine and Russia are engaged in intermittent negotiations to end a brutal war now in its third week. But despite signs of progress, Western officials have little optimism that the talks have reached a serious stage or even confronted the most difficult issues.

The president of Ukraine, Volodymyr Zelensky, has raised hopes with recent statements that seem to accept that his country will not be a part of NATO, despite the alliance’s promise in 2008 to accept it one day and even though the Ukrainian constitution was amended three years ago to make membership in both NATO and the European Union national goals.

A form of neutrality for Ukraine without NATO membership would seem to satisfy a key Russian demand, though only one of them. And any form of neutrality must come with security guarantees against further Russian aggression, the Ukrainians say. But who would provide such guarantees, and, if some guarantors are NATO members, how that would be fundamentally different from actual membership in the alliance, are only some of the fundamental questions outstanding.

On Wednesday, Mr. Zelensky said neutrality must include reliable guarantees that protect Ukraine from future threats. “We can and must defend our state, our life, our Ukrainian life,” he said. “We can and must negotiate a just but fair peace for Ukraine, real security guarantees that will work. Patience is needed.”

But Moscow has also demanded that Ukraine accept the loss of Crimea, annexed by Russia in 2014, and accept that a large chunk of the country in the east — the entire regions of Donetsk and Luhansk, parts of which are occupied by Russian-backed separatists — become independent republics, as Vladimir V. Putin, the Russian president, has decreed.

Ukraine rejects such a dismembering of its country, so it is difficult for now to see where a compromise might be found.

As a senior NATO official suggested, negotiations only work, as they finally did in Bosnia, when a conflict reaches a stalemate or one side wins. Neither Russia nor Ukraine is yet ready to stop fighting — Russia in its quest to seize Ukraine’s seacoast, main cities and the capital, Kyiv; or Ukraine to resist. Even if Russia’s advances have slowed, Mr. Putin gives no indication that his military or political goals have changed.

Secretary of State Antony J. Blinken said Thursday that the United States saw no sign that Mr. Putin was prepared to stop his military efforts.

“From where I sit, diplomacy obviously requires both sides engaging in good faith to de-escalate,” he said. “The actions that we’re seeing Russia take every single day, virtually every minute of every day, are in total contrast to any serious diplomatic effort to end the war.”

Various countries are making efforts to mediate between Russia and Ukraine, most notably Turkey and Israel, which are generally seen as having less fraught ties to both countries than Germany and France, which have also tried to make overtures to Mr. Putin. But efforts at basic and temporary cease-fires for civilians to escape the fighting around cities like Kharkiv and Mariupol have been difficult to achieve.

On Friday, it was Mr. Putin who complained in a call with the German chancellor, Olaf Scholz, that Ukraine was “trying to drag out the negotiation process by putting forward new unrealistic proposals” and accused Ukraine of war crimes.

Mr. Putin said Russia was “ready to propose a search for solutions in line with its well-known principled approaches” in a fourth round of talks. But even a negotiated cease-fire seems a distant prospect, let alone a lasting peace.

So far, according to a senior Ukrainian official, Russia’s demands are mostly unacceptable.

In essence, he said, Russia is demanding that the Ukrainian Parliament vote to enshrine the country’s neutrality, downgrade its army to 50,000 troops or fewer, pledge not to host any foreign military bases, and accept Russian sovereignty in Crimea and the independence of the entire Donbass region, which includes Donetsk and Luhansk.

Only then, the official said, would Russia agree to withdraw from other territory it has already occupied.

Ukraine, the official said, won’t agree to anything unless Russia first withdraws its forces, or to a military that small, which is less than a quarter of its prewar standing force. But it is willing to accept some form of demilitarized zone of some 50 to 100 kilometers on either side of the border, the official said.

The Ukrainians also want an international peacekeeping force in Ukraine, with its sovereignty guaranteed — and not simply “assured,” as in the 1994 Budapest Memorandum, in which the country agreed to give up its nuclear weapons inherited from the Soviet Union. And they want those security guarantees signed by the permanent members of the U.N. Security Council — the United States, Britain, China, France and Russia — plus Turkey and Germany.

That would commit the key members of NATO to fight for Ukraine should Russia (or any other country) invade. Given that NATO is unwilling to fight Russian troops in Ukraine now, or even to create a no-fly zone over Ukraine for risk of combat with Russia, it is hard to imagine that such guarantees could be agreed upon, the senior NATO official said.

Even on the issue of neutrality, there are complications enough, beyond the idea of altering the constitution. The Russian presidential spokesman Dmitry Peskov has suggested Austria as a model for Ukrainian neutrality. And Austrian officials have briefed Ukrainian officials, according to a senior Western diplomat. But given that Austria has no limits on the size of its own military forces, it is unlikely that its model will be acceptable to Russia.

Turkey is making its own mediating efforts. Turkey’s foreign minister, Mevlut Cavusoglu, traveled from Moscow to Lviv for separate talks with the Russian and Ukrainian foreign ministers this week. He expressed hopes for progress on a cease-fire, and set up a telephone conversation Thursday between Mr. Putin and the Turkish president, Recep Tayyip Erdogan.

Another view of Russia’s demands emerged from that conversation. According to Mr. Erdogan’s senior aide and spokesman, Ibrahim Kalin, who was on the call, Mr. Putin is also insisting on Russian again becoming an official language in Ukraine and on what he terms the “de-Nazification” of the country.

Mr. Kalin told the BBC that however offensive that last demand might be to Mr. Zelensky, who is Jewish and lost family in the Holocaust, it might be enough for Ukraine to pledge to condemn neo-Nazis and crack down on some of its far-right nationalist groups to fulfill it.

Mr. Kalin said a second category of demands was more difficult for Ukraine, involving territorial compromise, but he did not specify them.

The head of the Russian delegation, Vladimir Medinsky, said in Moscow on Friday that on the issue of demilitarization, the two sides are “somewhere halfway,” but did not disclose details.

A senior Western diplomat, briefed on the talks, suggested that neutrality and giving up Crimea would be easier for Ukraine than Russia’s other demands, like a further eastern partition and demilitarization. The diplomat confirmed that Mr. Putin appeared willing to talk to Mr. Zelensky, who seems to be trying to prepare Ukrainians for an eventual deal.

If accurate, Mr. Putin’s willingness to talk to Mr. Zelensky, whose ouster he originally demanded, is a form of progress. That is also an acknowledgment that the current Russian team negotiating with Ukraine is low-ranking and has little authority to settle the most difficult issues. So peace appears a very long way away.

Steven Erlanger reported from Brussels and Patrick Kingsley from Tbilisi, Georgia. Safak Timur contributed reporting from Istanbul.