Group of Seven (G7) leaders laid wreaths in the Japanese city of Hiroshima on Friday, almost 78 years after it was attacked with a nuclear bomb, in a sombre start of a summit expected to put more sanctions on Russia for its invasion of Ukraine.

Hiroshima’s legacy as the first place ever to be attacked with a nuclear weapon has taken on more urgency following Russia’s invasion of Ukraine and President Vladimir Putin’s talk of his readiness to use nuclear arms.

Ukrainian President Volodymyr Zelenskiy will travel to Japan to join the leaders of the world’s advanced democracies at their Hiroshima summit, a European Union source said.

G7 leaders are expected to announce tightened sanctions on Russia and debate strategy on a more than year-long conflict that shows no signs of easing.

The seven countries that have dominated the post-World War Two era ushered in after the destruction of Hiroshima and Nagasaki, also hit with a US nuclear bomb, are increasingly challenged by an ascendant China and unpredictable Russia.

Britain will announce a ban on Russian diamonds and imports of metals from Russia including copper, aluminium and nickel in support for Ukraine, it said in a statement.

Britain will also target an additional 86 people and companies from Putin’s military industrial complex, in addition to those involved in the energy, metals and shipping industries, it said.

European Council President Charles Michel said Europe would also restrict sales of Russian diamonds.

Officials were still hashing out the details of their final announcements on Russia as well as debating precise language on China, according to people from four of the nations involved.

Russia has said it is ready to use its nuclear arsenal to defend its “territorial integrity” if necessary.

Japanese Prime Minister Fumio Kishida, who represents Hiroshima in Japan’s lower house of parliament, said he chose the city for the summit to focus attention on arms control.

School children presented the G7 leaders with wreaths and they then solemnly placed them at a memorial park.

The United States is set to add 70 entities to its export blacklist, and to expand its sanctions authority to 300 entities as well as new sectors of the Russian economy, a senior US administration official said.

“You will hear a powerful statement of unity, strength and commitment in our response to Russia’s war of aggression,” the official said. “You will see new steps taken to economically isolate Russia and to weaken its ability to wage war.”

The goal is to close evasion loopholes in countries from Europe to Asia and the Middle East, target goods used by Russia in waging the war, reduce reliance on its energy exports and cut its access to the international financial system.