HIROSHIMA--World leaders landed in Hiroshima on Thursday for a Group of Seven meeting, the site of the world's first atomic bomb attack, with Russia’s war in Ukraine expected to be high on the agenda.

Japanese Prime Minister Fumio Kishida kicked off his summit diplomacy by meeting with U.S. President Joe Biden after his arrival at a nearby military base. He was due to hold talks with British Prime Minister Rishi Sunak a bit later in the day, before the three-day summit opens on Friday.

The Japan-U.S. alliance is the “very foundation of peace and security in the Indo- Pacific region,” Kishida told Biden in opening remarks.

“We very much welcome that the cooperation has evolved in leaps and bounds,” he said.

“When our countries stand together we stand stronger and I believe the whole world is safer when we do," Biden said.

The U.S. president exited Air Force One in heavy rain and briefly greeted troops on arrival at the nearby Marine Corps Air Station Iwakuni.

As G-7 attendees made their way to Hiroshima, Moscow unleashed yet another aerial attack on the Ukrainian capital. Loud explosions thundered through Kyiv during the early hours, marking the ninth time this month that Russian air raids have targeted the city after weeks of relative quiet.

“The crisis in Ukraine: I’m sure that’s what the conversation is going to start with,” said Matthew P. Goodman, senior vice president for economics at the Center for Strategic and International Studies.

Speaking to reporters aboard Air Force One, Jake Sullivan, the White House national security adviser, said there will be “discussions about the battlefield” in Ukraine and on the "state of play on sanctions and the steps that the G-7 will collectively commit to on enforcement in particular.”

G-7 leaders and invited guests from several other counties are also expected to discuss how to deal with China's growing assertiveness and military buildup as concerns rise that it could could try to seize Taiwan by force, sparking a wider conflict. China claims the self-governing island as its own and its ships and warplanes regularly patrol near it.

Security was tight in Hiroshima, with thousands of police deployed at numerous points throughout the city. A small group of protesters was considerably outnumbered by police as they gathered Wednesday evening beside the ruins of the Atomic Peace Dome memorial, holding signs including one which read “No G7 Imperialist Summit!”

In a bit of dueling diplomacy, Chinese President Xi Jinping is hosting the leaders of the Central Asian countries of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan for a two-day summit in the Chinese city of Xi’an starting Thursday.

During the meeting in Hiroshima, Kishida hopes to highlight the risks of nuclear proliferation. Leaders are expected to visit a memorial park that commemorates the 1945 atomic bombing by the U.S. that destroyed the city and killed 140,000 people.

North Korea’s nuclear program and a spate of recent missile tests have crystalized fears of an potential attack. So have Russia’s threats to use nuclear weapons in Ukraine. China, meanwhile, is rapidly expanding its nuclear arsenal.

The leaders are due to discuss efforts to strengthen the global economy and address rising prices that are squeezing families and government budgets around the world, particularly in developing countries in Africa, Asia and Latin America.

The debate over raising the debt limit in the U.S., the world's largest economy, has threatened to overshadow the G-7 talks. Biden plans to hurry back to Washington after the summit for debt negotiations, scrapping planned meetings in Papua New Guinea and Australia.

The British prime minister arrived in Japan earlier Thursday and paid a visit to the JS Izumo, a ship that can carry helicopters and fighter jets able to take off and land vertically.

During their bilateral meeting Thursday, Sunak and Kishida are expected to announce a series of new agreements on issues including defense; trade and investment; technology; and climate change, Sunak's office said.

The G-7 includes Japan, the United States, the United Kingdom, France, Germany, Canada and Italy, as well as the European Union.

A host of other countries have been invited to take part. The G-7 hopes to strengthen its members' ties with countries outside the world's richest industrialized nations, while shoring up support for efforts like isolating Russia.

Leaders from Australia, Brazil, India, Indonesia and South Korea are among those participating as guests. Ukrainian President Volodymyr Zelenskyy is expected to join by video link.