Ukrainian President Volodymyr Zelenskyy on Sunday wished Ukrainian military forces success in what he described as the "main battles" that are "coming soon."

Zelenskyy's statement came a day after he said at a news conference in Kyiv that Ukrainian forces will soon launch a counteroffensive, likely before F-16 fighter jets promised by Western allies arrive.

"Dear warriors, the main battles are coming soon. We must free our land and our people from Russian slavery,” Zelenskyy said at an event where he bestowed medals to members of the county’s Border Guard forces.

Ukrainian President Volodymyr Zelenskyy said the Ukrainian counteroffensive will start before Ukraine receives F-16 fighter jets sought from Western countries.

"Frankly speaking, it would help us a lot. But we also understand that we can't drag it [the counteroffensive] out, which is why we'll start before we receive F-16 [aircrafts] or other models," Zelenskyy said at a news conference for Scandinavian media held in Kyiv on Saturday, according to a script provided by Reuters.

He added, "But to calm Russia down with the fact that we'd still need a couple of months to train on the aircrafts and only then we'd start; No, this won't happen. We'll start and go forward, while at the same time, simultaneously, I think this is very important [to receive western fighter aircrafts.]"

He said Ukraine is "capable of putting an end to this war."

Also on Saturday, Ukraine's Foreign Minister Dmytro Kuleba said Ukraine received a signal from some countries about the readiness to start training Ukrainian pilots on F-16 fighter jets.

According to Kuleba, the F-16 fighter jet is the ideal aircraft due to its technical characteristics, although Kyiv does not overlook other aircraft, either. The minister added that the decisive word on issuing F-16s will be with the United States, because these are American fighters.

-ABC News' Edward Szekeres and Max Uzol

A Russian attack on a high-rise building in Uman has left 23 people dead. Among the dead were six children between the ages of one and 17 years old, according to the Ukrainian Minister of Internal Affairs, Ihor Volodymyrovych Klymenko.

Rescuers, policemen and volunteers managed to save 17 people from the rubble. Heavy machinery and special equipment were involved, according to officials.

Two more women are considered missing, officials said. But the search and rescue operation has concluded, officials said.

"My sincere condolences to the relatives of the deceased. We will punish this evil. We will not allow it to grow. We will definitely stand up and win," Klymenko said.

-ABC News' Tatyana Rymarenko

Russian airstrikes targeted several cities across Ukraine early Friday, killing at least 25 people, Ukrainian officials said.

The city of Uman in central Ukraine's Cherkasy Oblast was the worst affected. Several buildings were damaged or destroyed. One of the strikes hit an apartment building, killing at least 23 people, including four children, and injuring another 18 people, according to Cherkasy Oblast Gov. Ihor Taburets. The attack happened at around 4:30 a.m. local time, when most people would have been asleep. An entire section of the nine-story building collapsed, with 27 apartments completely destroyed. There were 109 people who lived in that part of the building, according to Ukrainian police. Rescue teams were expected to spend all day and night searching for survivors in the rubble.

It was the deadliest single attack on civilians in Ukraine since January.

Dnipro, Ukraine's fourth-largest city and a major industrial hub located in southeastern Dnipropetrovsk Oblast, was hit by "high-precision" strikes in the early morning hours, leaving a woman and a 3-year-old child dead, according to Dnipro Mayor Boris Filatov.

Russian strikes also targeted Kyiv, Ukraine's capital and largest city, but there were no reports of any casualties or damages. It was the first such attack on the capital in 51 days, according to the Kyiv City Military Administration. Preliminary data shows 11 cruise missiles and two drones were destroyed in Kyiv's airspace, the city military administration said.

-ABC News' Yulia Drozd, Will Gretsky, Natalia Kushnir and Joe Simonetti

The United States announced an additional $2 billion military aid package for Ukraine on Friday, as the Eastern European country marks the one-year anniversary of Russia's full-scale invasion.

The new aid package includes more missiles for Ukraine's U.S.-supplied High Mobility Artillery Rocket Systems (HIMARS), additional 155mm artillery ammunition, more Switchblade one-way drones and other military equipment, according to the U.S. Department of Defense.

"One year into a war of aggression waged by a permanent member of the U.N. Security Council, our allies and partners worldwide stand united and resolute," U.S. Secretary of Defense Lloyd Austin said in a statement. "Putin's reckless, illegal war is not just an all-out assault on Ukraine's sovereignty and a historic threat to European security. It is also a direct attack on the system of rules, institutions, and laws that the world built at such great cost after World War II -- a system that rejects aggression and respects the rights of all countries, big and small."

The additional aid is being provided under the Ukraine Security Assistance Initiative (USAI) plan, meaning this equipment and artillery have to be made from scratch before being delivered, which will take time. This is different from the other aid packages that come from existing U.S. military stockpiles and get delivered faster.

With the new aid package, the Biden administration has now provided $31.8 billion in assistance to Ukraine since Russia's war began on Feb. 24, 2022.

"Putin thought that Ukraine’s defenses would collapse, that America's resolve would falter, and that the world would look the other way. He was wrong," Lloyd said. "One year later, Ukraine's brave defenders have not wavered, and neither has our commitment to support them for as long as it takes. Despite the Kremlin's campaign of cruelty, the people of Ukraine have shown stunning bravery, skill, and fortitude. Today and every day, we stand by the courageous Ukrainians fighting to defend their country, and we mourn with those who have lost their loved ones in Moscow's monstrous and unnecessary war."

"Difficult times may lie ahead, but let us remain clear-eyed about what is at stake in Ukraine," he added. "And let us remain united in purpose and in action -- and steadfast in our commitment to ensure that a world of rules and rights is not replaced by one of tyranny and turmoil."

-ABC News' Luis Martinez