Turkey is beginning the process of ratifying Finland's application to join NATO, Turkish President Recep Tayyip Erdogan said Friday, 10 months after both Finland and Sweden applied to become NATO members in the wake of Russia’s invasion of Ukraine.

"At a critical time for our security, this will make our alliance stronger and safer," NATO Secretary General Jens Stoltenberg said in a statement.

The breakthrough came as Finnish President Sauli Niinisto was in Ankara, Turkey, to meet with Erdogan.

Erdogan said Finland fulfilled its part of the agreements and therefore he saw no reason to further delay the ratification process. Erdogan did not provide an update on Sweden's bid.

National security adviser Jake Sullivan said in a statement, "We encourage Türkiye to quickly ratify Sweden’s accession protocols as well. In addition, we urge Hungary to conclude its ratification process for both Finland and Sweden without delay. … The United States believes that both countries should become members of NATO as soon as possible."

-ABC News' Will Gretsky

The International Criminal Court has issued an arrest warrant for Russian President Vladimir Putin, saying in a statement Friday that Putin is "allegedly responsible for the war crime of" unlawfully deporting children from occupied areas of Ukraine and bringing them to Russia.

The ICC also issued an arrest warrant for Maria Lvova-Belova, Russia's presidential commissioner for children's rights, alleging she carried out the same war crime.

Russian Foreign Ministry spokeswoman Maria Zakharova said in a statement that the arrest warrants "have no meaning for the Russian Federation" and "are legally null and void."

Andriy Yermak, head of the Office of the President of Ukraine, tweeted that the arrest warrants are "just the beginning."

Russia has committed a "wide range of war crimes" and possible crimes against humanity in Ukraine, according to a new United Nations-backed investigation.

"The body of evidence collected shows that Russian authorities have committed a wide range of violations of international human rights law and international humanitarian law in many regions of Ukraine and in the Russian Federation," the human rights report by the Independent International Commission of Inquiry on Ukraine stated. "Many of these amount to war crimes and include willful killings, attacks on civilians, unlawful confinement, torture, rape, and forced transfers and deportations of children."

Additionally, Russian attacks on Ukraine's energy-related infrastructure and use of torture "may amount to crimes against humanity," the report concluded.

The commission said it conducted interviews with nearly 600 people, inspected graves, destruction and detention sites and consulted satellite imagery and photographs as part of its investigation.

Poland plans to deliver four MiG-29 fighter jets to Ukraine "in the coming days," Polish President Andrzej Duda said at a press conference on Thursday.

The move will make Poland the first NATO member to supply fighter planes to Ukraine, the Associated Press reported.

The latest news shortens the timeline announced earlier this week by Polish Prime Minister Mateusz Morawiecki, who had said they might send the Soviet-designed fighter jets to Ukraine in the next four to six weeks.

The Russian oligarch behind the Wagner private paramilitary group fighting for the Kremlin in Ukraine is threatening a mutiny if his forces are not resupplied with ammunition soon.

Yevgeny Prigozhin, owner and curator of the Wagner group, penned a letter to Russian Defense Minister Sergei Shoigue, demanding ammunition be provided to his forces on the battlefield.

In the letter, Prigozhin wrote that if supply problems are not fixed fast, he will complain to Russian President Vladimir Putin and his mercenaries would abandon their positions in Bakhmut, Ukraine, where heavy fighting has been going on for weeks, The Moscow Times reported.

“I appeal to Shoigu with a request to immediately issue ammunition. In case of refusal, I consider it necessary to convey to the Supreme Commander-in-Chief information about the existing problem in order to make a decision and about the advisability of further presence of Wagner PMC in Bakhmut in the conditions of a shortage of ammunition," Prigozhin wrote.

He added, "If the deficit is not replenished ... we will be forced to withdraw part of the units from this territory, and then everything else will crumble. Therefore, the bell is already ringing -- it is called an alarm."

Emphasizing the urgency, Prigozhin noted that Ukraine is planning to launch a counteroffensive soon.

There was no immediate public response from Shoigu or the Kremlin.

"We need to stop deceiving the population and telling that everything is fine with us," Prigozhin wrote. "I must honestly say: Russia is on the brink of disaster. If these screws are not adjusted today, the 'aircraft' will crumble in the air."