Ukraine’s lead negotiator, Mykhailo Podolyak, said Wednesday he believes the talks with Russia are absolutely "real" and that the Kremlin is not trying to use them to "stall for time" in order to regroup.

Podolyak, a senior aid to Ukraine's President Volodymyr Zelenskyy, told ABC News in an interview that he believes the Russians are looking to make a deal, but he warned Ukraine believes it's possible it may take months.

He said Russia has stopped issuing ultimatums and is now in the process of seeing how far it has to lower its goals.

Asked if Ukraine is ready to give up its ambitions to join NATO, Russia's key demand, Podolyak called on the U.S. to take the lead in forming a broader alliance that would give Ukraine security guarantees.

Zelenskyy has made it clear Ukraine is ready to potentially give up NATO membership, provided it gets security guarantees from Western countries that would protect it from a future Russian invasion.

When asked what that would look like, Podolyak suggested a potential security guarantee could be the U.S. and allies putting in writing that, in case of any future aggression from Russia, a no-fly zone would be put in place.

He has suggested that some NATO countries may be prepared to give those guarantees separate to NATO.

Podolyak also denied reports from several newspapers that claimed Russia and Ukraine are discussing a 15-point peace plan in which Ukraine would give up its NATO ambitions and accept some limits on its military in return for security guarantees from western countries.

He said for now, Russia and Ukraine both have drafts and Russia is leaking some of its drafts, pretending that it is a deal close to being signed.

-ABC News' Patrick Reevell

Russian President Vladimir Putin told his cabinet on Wednesday that Russia will require payments for natural gas in rubles, saying he will refuse to accept payments in "compromised currencies," including the dollar and the euro, according to Russia's state-run news agency, TASS.

Putin said Russia will continue to supply natural gas to other countries.

"I made the decision to implement within the shortest possible time the package of measures to transfer payments - we will start with that - for our natural gas supplied to the so-called ‘unfriendly’ states to Russian rubles," Putin said.

-ABC News' Christine Theodorou

European Commission President Ursula von der Leyen on Wednesday accused Russia's President Vladimir Putin of blocking hundreds of ships filled with wheat in the Black Sea.

"Our continent is being rocked by a tectonic shift not seen since the fall of the Berlin Wall. The consequences of this war on Europe's security architecture will be far-reaching. And I'm not just talking about security in military terms, but also energy security and even food security are at stake," she said in a speech to the European Commission.

Von der Leyen added: "The effects of the Russian war go beyond energy of course. They are also disrupting vital food supplies and driving food prices up."

The consequences of this disruption will be felt from Lebanon, Egypt and Tunisia to Africa and the Far East, according to von der Leyen.

"We should not forget that Ukraine alone provides more than half of the world food programs' wheat supply. The shelling and the bombing makes it impossible for Ukrainian farmers to sow," she said.

"I call on Putin to let those ships go. Otherwise, he will not only be responsible for a war and death, but also for famine and hunger. Let these ships go," von der Leyen added.

-ABC News' Christine Theodorou

NATO Secretary-General Jens Stoltenberg told reporters Wednesday that he expects allies to announce major increases to forces in the eastern part of the defense alliance at Thursday's summit.

Stoltenberg said the first step would be the deployment of four new NATO battle groups in Bulgaria, Hungary, Romania and Slovakia. With the existing forces in place, there will be eight multi-national battle groups all along the eastern flank, from the Baltic to the Black Sea.

"We face a new reality for our security, so we must reset our deterrence and defense for the longer term," Stoltenberg said.

Stoltenberg said he expects allies will agree to provide additional support to Ukraine, including cybersecurity assistance and equipment to help Ukraine protect against chemical, biological, radiological and nuclear threats.

He added that NATO has a responsibility to make sure the conflict does not escalate beyond Ukraine, as "this will cause even more death and even more destruction."

Stoltenberg also called on Belarus to end its complicity in the war.

-ABC News' Christine Theodorou

All Russian troops have left the Ukrainian cities of Kyiv and Chernihiv, withdrawing north toward the borders of Belarus and Russia to consolidate before likely redeploying to the Donbas region in eastern Ukraine, a senior U.S. defense official told reporters Wednesday.

But even with the Russians gone, the territory remains treacherous.

"There are some indications that they left behind mines and things like that, so the Ukrainians are being somewhat careful in some areas north of Kyiv as they begin to clear the ground and clear the territory and re-occupy it," the official said.

While the U.S. hasn't yet seen these troops redeploy elsewhere in Ukraine, it'll likely happen soon, according to the official. Ukrainian forces are preparing for a major fight in Donbas, the official said.

The official also said the Pentagon is "monitoring" an apparent nitric acid explosion in Ukraine's Luhansk region, which Russia blamed on Ukraine.

"We've seen the Russians claim that this was a Ukrainian attack on this. We do not believe that is true," the official said. "We do believe that the Russians are responsible, but exactly what they used when they did it, why they did it, what the damage is, we just don't have that level of detail," the official said.

The official also noted that a small number of Ukrainians currently in the U.S. for "professional military education" were pulled aside for a couple days of training on Switchblade drones, which the U.S. is sending overseas as part of its military aid, according to the official.

"Although it's not a very difficult system to operate, we took advantage of having them in the country to give them some rudimentary training on that," the official said.

-ABC News' Matt Seyler