World leaders landed Thursday for a Group of Seven meeting in Hiroshima, 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 began his summit diplomacy by meeting US President Joe Biden after his arrival at a nearby military base. He was due to hold talks with British Prime Minister Rishi Sunak later in the day before the three-day gathering of the leaders of the world’s rich democracies begins on Friday.

The Japan-US alliance is the “huge foundation for peace and security in the Indo-Pacific region,” Kishida told Biden in an opening statement.

“We very much welcome that cooperation has developed by leaps and bounds,” he said.

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

The US president exited Air Force One and briefly greeted troops at nearby Marine Corps Air Station Iwakuni.

As G-7 participants made their way to Hiroshima, Moscow unleashed another airstrike on the Ukrainian capital. Loud explosions thundered through Kiev in the early hours, marking the ninth time this month that Russian airstrikes have targeted the city after weeks of relative calm.

“The crisis in Ukraine: I’m sure that’s what the conversation will 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’s national security adviser, said there will be “discussions about the battlefield” in Ukraine and about “the state of sanctions and the actions that the G-7 will collectively take particularly on execution.”

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 fears mount that it could try to take Taiwan by force, triggering 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 officers deployed in many locations throughout the city. A small group of protesters were significantly outgunned by police as they gathered Wednesday night next to the ruins of the Atomic Peace Dome memorial, holding signs including one that 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. The leaders are expected to visit a memorial park commemorating the 1945 US atomic bombing that destroyed the city and killed 140,000 people.

North Korea’s nuclear program and a series of new missile tests have crystallized fears of a potential attack. It also has Russia’s threat to use nuclear weapons in Ukraine. China, meanwhile, is rapidly expanding its nuclear arsenal.

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

The debate over raising the debt limit in the US, the world’s largest economy, has threatened to overshadow the G-7 talks. Biden plans to rush 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 visited the JS Izumo, a ship capable of carrying helicopters and fighter jets that can take off and land vertically.

During their bilateral meeting on Thursday, Sunak and Kishida are expected to announce a range of new agreements on issues including defence; 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 number of other countries have been invited to participate. The G-7 hopes to strengthen its members’ ties with countries outside the world’s richest industrialized nations while gaining support for efforts such as isolating Russia.

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