Speaking by video to the UN General Assembly meeting of world leaders hours after Russian President Vladimir Putin's announcement, Zelenskyy insisted his country would prevail in repelling Russia's attack and forcing its troops out.

"We can return the Ukrainian flag to our entire territory. We can do it with the force of arms," the president said. "But we need time."

Putin's decree Wednesday about the mobilization was sparse on details.?

Officials said as many as 3,00,000 reservists could be tapped. It was apparently an effort to seize momentum after a Ukrainian counteroffensive this month retook swaths of territory that Russians had held.

But the first such call-up in Russia since World War II also brings the fighting home in a new way for Russians and risks fanning domestic anxiety and antipathy toward the war. Shortly after Putin's announcement, flights out of the country rapidly filled up, and hundreds of people were arrested at antiwar demonstrations across the country.

A day earlier, Russian-controlled parts of eastern and southern Ukraine announced plans for referendums on becoming parts of Russia. Ukrainian leaders and their Western allies consider the votes illegitimate.

Zelenskyy didn't discuss the developments in detail. But he suggested any Russian talk of negotiations is only a delaying tactic, and that Moscow's actions speak louder than its words.

"They talk about the talks but announce military mobilization. They talk about the talks but announce pseudo-referendums in the occupied territories of Ukraine,” he said.

Russia hasn't yet had its turn to speak at the gathering.?

Putin, who is not attending the event, has said he sent his armed forces into Ukraine because of risks to his country's security from what he considers a hostile government in Kyiv; to liberate Russians living in Ukraine — especially its eastern Donbas region — from what he views as the Ukrainian government's oppression; and to restore what he considers to be Russia's historical territorial claims on the country.

Zelenskyy's speech was striking not only for its contents but also its context. It took place after the extraordinary mobilization announcement. It was the first time he addressed the world's leaders gathered together since Russia invaded in February.?

It wasn't delivered at the august rostrum where other presidents, prime ministers and monarchs speak — but instead by video from a nation at war after Zelenskyy was granted special permission to not come in person.

He appeared as he has in many previous video appearances — in an olive green T-shirt. He sat at a table with a Ukrainian flag behind his right shoulder and large image of the UN flag and Ukraine's behind his left shoulder.

The leader opined that Moscow wants to spend the winter preparing its forces in Ukraine for a new offensive, or at least preparing fortifications while mobilizing more troops in the largest military conflict in Europe since World War II.

"Russia wants war. It's true. But Russia will not be able to stop the course of history," he said, declaring that "mankind and the international law are stronger" than what he called a "terrorist state".

Laying out various "preconditions for peace" in Ukraine that sometimes reached into broader prescriptions for improving the global order, he urged world leaders to strip Russia of its vote in international institutions and UN Security Council veto, saying that aggressors need to be punished and isolated.

The fighting has already prompted some moves against Russia in UN bodies, after Moscow was able to veto a demand that to stop its attack on Ukraine days after it began.

The veto particularly galled a number of other countries and led to action in the broader General Assembly, where resolutions aren't binding but there are no vetoes.

The assembly voted overwhelmingly in March to deplore Russia's aggression against Ukraine, call for an immediate cease-fire and withdrawal of all Russian forces, and urge protection for millions of civilians. The next month, a smaller but still commanding number of members voted to suspend Russia from the UN Human Rights Council.

Zelenskyy's speech was one of the most keenly anticipated at a gathering that has dwelled this year on the war in his country. But it wasn't the first time the first-term president has found himself in the spotlight at the assembly's annual meeting.

At last year's General Assembly, Zelenskyy memorably compared the UN to "a retired superhero who's long forgotten how great they once were" as he repeated appeals for action to confront Russia over its 2014 annexation of Ukraine's Crimean peninsula and its support for the separatists.?