The NATO summit in Vilnius showed that the NATO "alliance has finally returned to the schemes of the Cold War," the Russian Foreign Ministry said in a statement Wednesday.

"NATO consistently lowers the threshold for the use of force and strengthens the nuclear component in military planning," the statement added.

The Russian Foreign Ministry also noted NATO countries "promised to continue supplying more and more long-range weapons to Kyiv," saying they are doing so in order to "prolong the conflict."

-ABC News' Tanya Stukalova

Ukrainian President Volodymyr Zelenskyy said he received assurances that Ukraine will become a member of NATO and told reporters he believes it will happen "as soon as the security situation is stabilized," when answering questions after the conclusion of the NATO summit in Vilnius, Lithuania, on Wednesday.

When asked what Zelenskyy got out of the summit, he said he received "support from the leaders and an unambiguous statement that Ukraine will be in NATO."

"I believe that we will be in NATO as soon as the security situation is stabilized. In simple terms, the moment the war is over, Ukraine will definitely be invited to join NATO and Ukraine will definitely become a member of the alliance. I have not heard any other opinion today," Zelenskyy said.

-ABC News' Ellie Kaufman

Wagner forces are turning over weapons and military equipment to the Russian Armed Forces, the country's defense ministry said Wednesday.

More than 2,000 pieces of equipment and weapons were transferred to the Russian Armed Forces from Wagner forces, including hundreds of tanks, air defense systems, self-propelled artillery mounts, armored personnel carriers and more, the defense ministry said.

Among the equipment, dozens of units have never been used in combat before.

Russian forces also received more than 2,500 tons of various ammunition and about 20,000 small arms, the defense ministry said.

Separately, the Belarusian Interior Ministry has "begun talks seeking to invite Wagner Group members to train its troops," Interfax, a Russian news agency, reported Wednesday.

-ABC News' Ellie Kaufman

Ukrainian President Volodymyr Zelenskyy said his in-person meeting with U.S. President Joe Biden in Lithuania’s capital on Wednesday was "very good" and "powerful."

Zelenskyy took to Twitter after their meeting ended in Vilnius, saying it lasted "twice as long as planned" and "was as meaningful as it needed to be."

"If the protocol had not stopped the meeting, we would have talked even longer," he tweeted.

Zelenskyy said their meeting covered "all the topics," including long-term support for Ukraine, weapons, politics and NATO membership.

"We clearly see how to end this war with our common victory," he added. "Thank you, Mr. President!"

In the wake of Saturday's short-lived attempted rebellion against the Kremlin by the Wagner private military company, Mikhail Khodorkovsky, an exiled oligarch considered one of Putin’s best-known opponents, told ABC News he supports the mutiny and encourages Russians to back the leader of the mercenary group.

Once Russia’s richest man, Khodorkovsky, a Putin opposition activist, spent 10 years imprisoned after he challenged Putin, his case now considered a foundational moment for Putin’s regime.

When Wagner founder Yevgeny Prigozhin and his fighters marched on Moscow Saturday before making a sudden about-face, Khodorkovsky was notable among Russia’s pro-democracy opposition in calling on people to support Prigozhin, arguing that allowing him to remove Putin would create an opportunity for the democrats.

Khodorkovsky told ABC News he believed Prigozhin’s actions were a real coup attempt and that it had “seriously undermined” Putin’s power. He predicted that similar opportunities to collapse the regime will be launched soon.

"The blow to Putin’s reputation, to the authorities’ reputation, was absolutely fantastical," Khodorkovsky said. "Putin’s government today is, without a doubt, strongly undermined by what happened -- his authority, his ability to control the security services is seriously undermined."

Khodorkovsky said Prigozhin’s march on Moscow had undermined Putin’s popularity, showing neither ordinary Russians nor the security services were prepared to act to protect him.

“Along the entire route of Wagner's columns, no one in any way tried to hinder him (Prigozhin). Even the security forces did not try to stop him," Khodorkovsky said. “It showed that, in fact, inside the country, Putin has an absolute void."

Khodorkovsky said he did not support Prigozhin himself -- considering him a "war criminal" -- but that the democratic opposition should have sought to help him overthrow Putin, and then taken power from him after.

Khodorkovsky criticized other parts of the anti-Kremlin opposition who attacked him for calling on people to assist Prigozhin, saying he believed the opposition had “slept through” the opportunity and suggesting it should have sought to stage a rebellion in Moscow at the same time.

"There will definitely now be more such opportunities because of Putin’s weakening. But the next time we need to simply be more ready," said Khodorkovsky, who is living in exile in England. "If an uprising had started in Moscow to meet Prigozhin then a situation could have developed quite differently.

ABC News' Patrick Reevell