Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

Friday marked the 100th day since Russian forces invaded neighboring Ukraine.

In a statement, the Ukrainian Ministry of Foreign Affairs described the "full-scale invasion" as a "continuation of Russia’s aggressive actions it unleashed 8 years ago by occupying Crimea and parts of territories of Donetsk and Luhansk regions."

"Today, our people defend not only their right to exist and live in an independent state, but the security of Europe and the whole democratic world," the ministry said. "Every day our defenders, at the cost of their own lives, bravely repel Russia’s war machine and fight for freedom and peaceful future of the continent."

"For 100 days of war, the Kremlin has failed to reach its main goal -- conquest of Ukraine," the ministry added. "Instead, Russia has become the most sanctioned state in the world, and its activities within international organizations and participation in international events have been significantly limited or stopped. The Ukrainian army is bravely holding the line and has liberated territories in a number of regions. Ukraine is determined to have a complete victory over the Russian invader."

The ministry thanked the "dozens of countries around the world who provide significant support" to Ukraine. It also called on the international community to support the establishment of a special tribunal to investigate alleged war crimes committed by Russian forces in Ukraine.

"In order to stop Russia's crimes against the Ukrainian people, destruction of our economy and blackmail of the whole world by famine, consistent support for Ukraine should continue. Assistance to our state today is the best investment in peace and sustainable development of all mankind," the ministry said. "The main pillars for our victory remain unchanged: maximum sanction pressure on Russia, deliveries of necessary weapons and granting Ukraine the status of candidate on the way to full-fledged EU membership."

Meanwhile, Russian Ministry of Foreign Affairs spokesperson Maria Zakharova applauded progress that's been made in the so-called special military operation in Ukraine.

"The special military operation will be continued until all of its objectives declared by the Russian administration, including denazification and demilitarization of Ukraine, are achieved," Zakharova said at a press briefing Friday. "A lot has been done in this area: militants of the Azov nationalistic formation have surrendered in Mariupol and the liberation of Donbas has been consistently carried out."

Russia now controls over 46,300 square miles of Ukraine, which accounts for about 20% of Ukraine's territory, according to Ukrainian President Volodymyr Zelenskyy.

Since Russia's invasion began, Russian forces have gained control of over 16,602 square miles, or roughly 7% of Ukraine's territory -- an area that's comparable to the size of the Netherlands, Zelenskyy said Thursday in a speech to the Chamber of Deputies of Luxembourg. Combined with the territory from Russia's annexation of Crimea in 2014 and the war in the Donbas region, Russia's control of Ukraine now accounts for 20% of its territory, he said.

-ABC News' Christine Theodorou

Since the start of Russia's invasion, the Ukrainian first lady has been in hiding with her two children. A difficult question her 9-year-old son keeps asking is when the war will end, Olena Zelenska said in an exclusive interview with ABC News.

"Unfortunately, I don't think any Ukrainian would be able to answer that question," Zelenska told "Good Morning America" co-anchor Robin Roberts in her first televised solo interview since the invasion began.

In discussing the state of the conflict nearly 100 days after Russian President Vladimir Putin launched a "special military operation" in Ukraine, Zelenska said that conceding territory to Russia won't stop the war.

"You just can't concede ... parts of your territory. It's like conceding a freedom," Zelenska, 44, said in the interview, airing on "Good Morning America" Thursday. "Even if we would consider territories, the aggressor would not stop at that. He would continue pressing, he would continue launching more and more steps forward, more and more attacks against our territory."

The interview with Zelenska will air Thursday on "Good Morning America" and across ABC News. "Good Morning America" airs at 7 a.m. on ABC.

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First Lady of Ukraine discusses state of war with Robin Roberts

In an exclusive interview with ABC News, Olena Zelenska spoke about the ongoing conflict with Russia and where the Ukrainian people currently stand as a country.

Russian forces have taken control of most of Sieverodonetsk in eastern Ukraine, the U.K. Ministry of Defense said Thursday in an intelligence update.

"The main road into the Sieverodonetsk pocket likely remains under Ukrainian control but Russia continues to make steady local gains, enabled by a heavy concentration of artillery," the ministry said. "This has not been without cost, and Russian forces have sustained losses in the process."

Sieverodonetsk, an industrial hub, is the largest city still held by Ukrainian troops in the contested Donbas region of Ukraine's east, which comprises the self-proclaimed republics in Luhansk and Donetsk oblasts.

"Crossing the Siverskyy Donets River -- which is a natural barrier to its axes of advance –- is vital for Russian forces as they secure Luhansk Oblast and prepare to switch focus to Donetsk Oblast," the ministry added. "Potential crossing sites include between Sieverodonetsk and the neighbouring town of Lysychansk; and near recently-captured Lyman. In both locations, the river line likely still remains controlled by Ukrainian forces, who have destroyed existing bridges."

Sievierodonetsk and Lysychansk are the last major cities in the Luhansk area still controlled by Ukraine.

"It is likely Russia will need at least a short tactical pause to re-set for opposed river crossings and subsequent attacks further into Donetsk Oblast, where Ukrainian armed forces have prepared defensive positions," the ministry added. "To do so risks losing some of the momentum they have built over the last week."