In an exclusive interview Monday with ABC News anchor David Muir, Ukraine President Volodymyr Zelenskyy said the path to peace is "more difficult than simply acknowledging" another ultimatum from Russian President Vladimir Putin.

Zelenskyy spoke with Muir from the Presidential Office in Kyiv and said he will stay in his country for the duration of the war.

"When the Kremlin says these three conditions to end the war … that you must give up on joining NATO, recognize Crimea as part of Russia and recognize the independence of those two separatist regions in the east … you say it’s a nonstarter, not willing to [accept] those three conditions right now?" Muir asked.

Zelenskyy responded, "It is more difficult than simply acknowledging them ... this is another ultimatum and we are not prepared for ultimatums."

He went on, "But we have the possible solution resolution for these three items, key items, what needs to be done is for President Putin to start talking. Start the dialogue instead of living in the information bubble without oxygen. I think that’s where he is. He is in this bubble. He’s getting this information and you don’t know how realistic that information is that he’s getting."

President Joe Biden is scheduled to hold a secure video teleconference Monday morning with leaders of France, Germany and the United Kingdom to discuss the latest developments regarding Russia and Ukraine, according to the White House.

Biden is expected to be in the White House Situation Room when he participates in a teleconference with French President Emmanuel Macron, German Chancellor Olaf Scholz and British Prime Minister Boris Johnson, according to the White House.

The teleconference will be closed to the press and will occur after Biden received his daily intelligence briefing, the White House said.

-ABC News' Ben Gittleson

Russian President Vladimir Putin spoke with European Council President Charles Michel on Monday and according to a Kremlin readout of the conversation, falsely claimed Russian forces are “taking all possible measures to save the lives of civilians" in Ukraine.

Putin also repeated the Russian military’s claim that Ukrainian "nationalists" are preventing humanitarian corridors from being opened to allow the evacuation of civilians. But Ukrainian authorities have claimed efforts to evacuate its citizens out of the country have been disrupted by Russian forces shelling the humanitarian corridors Moscow agreed to in a cease-fire.

"The main threat comes from nationalist formations, which essentially use the tactics of terrorists, hiding behind the civilian population," Putin told Michel, according to the report.

The Russian president "called on the European Union to make a real contribution to saving people's lives, to put pressure on the Kyiv authorities and force them to respect humanitarian law," the Kremlin said in a statement.

-ABC News' Patrick Reevell

Ukrainian Minister of Foreign Affairs Dmytro Kuleba on Monday called for NATO to enforce a no-fly zone over Ukraine, saying Russian planes were targeting civilians.

"The Russian Air Force dominates in the skies and continues bombing our cities and killing many civilians," Kuleba told George Stephanopoulos on "Good Morning America."

U.S. and NATO officials have rejected calls from Ukrainian officials to impose a no-fly zone, saying doing so could provoke Russia, perhaps pulling other European countries and NATO members into the conflict. The U.S. and NATO have offered other military aid, including a possible deal to send aircraft to Ukraine.

"We believe that the rejection of the idea of the no-fly zone is based in the lack of confidence in the strength of NATO as an alliance," Kuleba said. "Because the military might of NATO is incomparably bigger compared to Russia. So why would Russia dare to shoot down a NATO plane, knowing it is doomed, eventually doomed, if a war with NATO begins."

Kuleba over the weekend had urged the international community to help in the struggle against “Russian barbarians.” He posted a photo on Twitter on Sunday of an unexploded bomb, which he said landed on a residential building in Chernihiv.

U.S. Secretary of State Antony Blinken crossed the border into Ukraine Saturday after meeting with Ukrainian Foreign Minister Dmytro Kuleba at the Korczowa Border Crossing Point.

"The entire world stand with Ukraine," Blinken said, and Kuleba added that he hopes Ukrainians will see this as a "clear manifestation that we have friends who literally stand by us."

Blinken said the sanctions imposed so far against Russia are "producing very, very concrete results" and that the pressure will "grow" until this "war of choice is brought to an end."

When asked directly about helping Kuleba with more firepower, Blinken said, "the support for Ukraine not only has been unprecedented, not only is going to continue, it's going to increase."

Kuleba said Ukraine "appreciates" sanctions that have been announced in the last week, but that more economic and political pressure and "necessary weapons," would "save many lives in Ukraine... many sufferings will be avoided."

Kuleba also said that they are “satisfied" with already arranged supplies of anti-tank weapons and ammunition, but that “it’s no secret” they still want fighter jets and air defense systems.

He also thanked the U.S. for sending stingers, and said they were used on Saturday.

"Just today we shot down three Russian attack aircrafts, which were bombing our cities with the use of stingers but we need -- so to say -- big air defense systems to ensure the safety of our skies. If we lose the skies, there will be much, much more blood on the ground,"Kuleba said.

In response to questions about NATO’s refusal to impose a no-fly zone over Ukraine, Kuleba said it’s a "sign of weakness," but stayed optimistic that they will change their minds.

"The time will come," he said.

-ABC News' Conor Finnegan and Justin Gomez