Ukrainian Defense Minister Oleksii Reznikov said Friday the military is "ready" to launch a counteroffensive against Russian forces.

"It's up to the general staff and the command," Reznikov said during a press briefing in Kyiv. "We will do it as soon as there is God's will, the weather and the commanders' decision."

Ukraine has received Patriot missile defense systems from the United States as well as Germany and the Netherlands. The Ukrainian military has been trained on how to use the systems and "mastered" them within weeks, according to Reznikov.

"The exact number of batteries, I'm sorry, I won't say," he added. "Let the enemy guess."

Meanwhile, Ukrainian Foreign Minister Dmytro Kuleba urged the world not to consider or call the anticipated counteroffensive "a decisive battle." Speaking at a press conference in Odesa on Friday, Kuleba said the decisive battle is the one that will lead to the liberation of all occupied Ukrainian territories.

-ABC News’ Will Gretsky

One person was killed and 23 people, including a child, were wounded in a Russian missile strike in Mykolaiv early Thursday, Ukrainian President Volodymyr Zelenskyy said.

The missile struck a block that had apartments, houses and a historic building, according to Zelenskyy.

"The terrorists will not get away with this yet another crime against humanity," the president said in a statement.

-ABC News' Will Gretsky

Ukrainian President Volodymyr Zelenskyy spoke with Chinese President Xi Jinping in what was the two leaders' first official contact since January 2022, before Russia's invasion of Ukraine.

Xi announced that he will send a special envoy to visit Ukraine and "other countries" to work on a political solution.

"I believe that this call, as well as the appointment of Ukraine's ambassador to China, will give a powerful impetus to the development of our bilateral relations," Zelenskyy said in a statement on Twitter.

The Chinese government's official position still refuses to call the war an "invasion."

The call between the two leaders is said to have lasted an hour, according to Zelenskyy's office.

"Before the full-scale Russian invasion, China was Ukraine's number one trading partner. I believe that our conversation today will give a powerful impetus to the return, preservation and development of this dynamic at all levels," Zelenskyy said in a statement.

-ABC News' Karson Yiu, Cindy Smith and Will Gretsky

At least two people were killed and 10 injured after a Russian missile hit a Ukrainian museum Tuesday, officials said.

The local history museum is located in the city center of Kupiansk, in the Kharkiv region.

"The terrorist country is doing everything to destroy us completely. Our history, our culture, our people," Ukrainian President Volodymyr Zelenskyy said on social media while sharing a video that showed the damaged building. "Killing Ukrainians with absolutely barbaric methods."

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."