President Volodymyr Zelensky of Ukraine landed in Japan on Saturday determined to urge the wealthiest democracies in the world to stick with him as Moscow bets on the West growing fatigued by the cost and consequences of the war.

Mr. Zelensky made a dramatic entry into Hiroshima, landing in a French plane after days in which Ukrainian and Japanese officials insisted, presumably for security reasons, that he would join the leaders at the Group of 7 summit only virtually. He was dressed in his signature hoodie, standing out from the coat-and-tie diplomatic crowd of this annual summit meeting.

Hours after Mr. Zelensky arrived in Japan, the Russian government said its forces had occupied the eastern Ukrainian city of Bakhmut. The city had become an important symbol of Ukrainian defiance and Russian determination, and its fall would both bolster and complicate Mr. Zelensky’s appeal for help.

Mr. Zelensky, American and British officials say, seems to sense that when he shows up in person, he can both break through American resistance to sending more powerful weapons, and pressure nations like India and Brazil that have stayed on the sidelines.

His presence could make it more difficult for them to maintain their stance as fence sitters, several officials said. And even as Mr. Zelensky consulted with countries already in his corner, he sat down with Narendra Modi, the prime minister of India, who was there as an observer, to make his case for support, much as he had done earlier in the week in Saudi Arabia.

“I think this is a unique opportunity” for Mr. Zelensky to have “exchanges with a lot of countries from the south and express your situation, express a message and share a view,” President Emmanuel Macron of France said. “I do believe it can be a game changer.”

Mr. Zelensky was expected to address the Group of 7 leaders on Sunday as part of his continued efforts to marshal more military aid for his country. He is making his appeals in a city that serves as a sobering reminder of the devastation that arises when a bitter war leads to the use of a nuclear weapon.

Mr. Zelensky plans to go to the peace park that has been built on the island that was ground zero for the explosion in 1945 that ushered in the age of nuclear weapons — an era that has returned amid episodic threats by the Russian president, Vladimir V. Putin, to turn to his own arsenal.

Even before he landed, Mr. Zelensky had won a significant victory: On Friday night President Biden told other leaders he would join the largely European effort to train Ukrainian pilots on how to fly the F-16 fighter jet. Reversing his previous stance, Mr. Biden said he would work with allies to begin providing the warplanes to Ukraine, weaning it from its dilapidated Soviet-era fighters.

Administration officials said they increasingly realized that sooner or later Ukraine would need the new fighters as part of a long-term program to deter Russia from invading anew, and decided they should get out ahead of the effort. But the planes would have little utility in the present stage of the war, where urban warfare rather than air warfare has dominated.

Mr. Zelensky arrived here just as the head of the Wagner paramilitary group said his forces had captured the devastated city of Bakhmut on Saturday, suggesting that the monthslong struggle to control it was over. The Ukrainian military rejected the claim by the mercenary group’s leader, Yevgeny V. Prigozhin, who is prone to making bombastic remarks.

Much of the discussion here in the past two days has focused on cracking down on sanctions evasion, as countries seeking to play both sides of the war — including India and the United Arab Emirates — have done nothing to curtail a black-market trade in semiconductors and materials needed by Russia to keep fighting the war.

Mr. Biden and Mr. Zelensky — and most of the core members of the Group of 7 — appear intent on maximizing Moscow’s pain until it comes to the bargaining table and retreats from Ukrainian territory. While they deny a new Cold War is underway, the surge in sanctions announced over the past two days seems a modern version of the containment strategy that guided the West’s confrontation with the Soviet Union, which collapsed more than three decades ago.

This was the first time Mr. Zelensky has taken his diplomatic tour to Asia, and he landed late Saturday afternoon in the city known to the world for having resurrected itself, in a monumental reconstruction task akin to what many believe Ukraine will have to undertake.

A red carpet had been rolled out on the tarmac of an airport in Hiroshima, where live footage on the public broadcaster, NHK, showed Mr. Zelensky stepping off a French plane in his olive green hoodie. He was immediately whisked away in a black sedan.

“Japan. G7. Important meetings with partners and friends of Ukraine,” Mr. Zelensky wrote on Twitter shortly after landing. “Security and enhanced cooperation for our victory. Peace will become closer today.”

Mr. Zelensky’s visit to Japan for the Group of 7 meeting followed the trip to Saudi Arabia, where he urged Arab leaders meeting there not to turn a “blind eye” to Russian atrocities in Ukraine.

His appearance was arranged after Mr. Zelensky expressed a “strong desire” to participate in the summit face to face, Japan’s Foreign Ministry said in a statement. The visit is the latest in a flurry of trips outside Ukraine to shore up support ahead of an anticipated Ukrainian counteroffensive.

The leaders — besides President Biden, they include the heads of government from Japan, Canada, Britain, France, Germany and Italy; and a top European Union official — will be talking over the weekend about all dimensions of Russia’s war in Ukraine. In addition to questions of when and how to provide Kyiv with the F-16 fighter jets, they may also discuss the possibility of negotiations over an armistice or peace treaty.

The G7 leaders have already pledged at the summit to toughen punishments on Moscow and redouble efforts to choke off funding for its war.

Mr. Biden has cut short his trip in order to return to Washington for debt and spending talks. The president had planned to fly from Japan to Papua New Guinea, before heading on to Sydney for a meeting of the so-called Quad: the United States, Australia, India and Japan.

Instead, the leaders of the Quad countries came to Mr. Biden, meeting him in Hiroshima on Saturday night.

Motoko Rich and Jim Tankersley contributed reporting.