U.S. President Joe Biden and Prime Minister Fumio Kishida used a guestbook message during an unprecedented visit to the Hiroshima Peace Memorial Museum on Friday to call for a nuclear weapons-free world, the Japanese government revealed Saturday.

“May the stories of this Museum remind us all of our obligations to build a future of peace,” Biden wrote, according to the Japanese Foreign Ministry. “Together let us continue to make progress toward the day when we can finally and forever rid the world of nuclear weapons. Keep the faith!”

Kishida, who on Friday won the endorsement of his fellow G7 leaders for an action plan intended to spur momentum for a nuke-free world, echoed Biden in his guestbook entry.