UNITED NATIONS (AP) — Ukrainian President Volodymyr Zelenskyy suggested Wednesday that Russia’s decision to mobilize some reservists showed that Moscow isn’t serious about negotiating an end to its nearly seven-month-long war.

Speaking by video to the U.N. 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 partial mobilization was sparse on details. Officials said as many as 300,000 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.

Zelenskyy 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 U.N. flag and Ukraine’s behind his left shoulder. He appeared to be in a conference room.

He 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.

“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.”

The war, the largest military conflict in Europe since World War II, has dominated the global gathering.

In a reflection of the circumstances, Zelenskyy wasn’t at the august rostrum where other presidents, prime ministers and monarchs speak at international diplomacy’s most prominent annual gathering. Instead, he got an exception to speak via video.

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 U.N. Security Council veto, saying that aggressors need to be punished and isolated.

The fighting has already prompted some moves against Russia in U.N. bodies. The move that galled a number of other countries and led to action this spring 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, members a smaller but still commanding number of members voted to suspend Russia from the U.N. Human Rights Council.

But as a permanent member of its most powerful entity, the Security Council, Russia was able to veto a demand to stop its attack on Ukraine days after it began.

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 of presidents, premiers, monarchs, and foreign ministers.

At last year’s General Assembly meeting, Zelenskyy memorably compared the U.N. 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.