President Joe Biden led tributes in the US following the assassination of Shinzo Abe, saying the former Japanese prime minister's "vision of a free and open Indo-Pacific will endure".
Mr Biden visited the residence of Koji Tomita, Japanese ambassador, in Washington to offer his respects and sign a condolence book.
"On behalf of the Biden family and all of America, we extend our heartfelt sympathy to the Abe family and the people of Japan," Mr Biden wrote.
“It is not only a loss to his wife and family and the people of Japan, it is a loss to the world. A man of peace and judgment, he will be missed."
Abe was shot on Friday while delivering a campaign speech on a street corner in Japan. He was transported by helicopter to a hospital where he was later pronounced dead.
Mr Biden condemned the assassination, saying "gun violence always leaves a deep scar on the communities that are affected by it".
The president also ordered that flags be flown at half-staff until July 10 as a "mark of respect" to the former prime minister.
"The longest serving Prime Minister in Japan's history, Abe Shinzo was a proud servant of the Japanese people and a faithful friend to the United States," Mr Biden wrote in a proclamation.
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In a separate statement, former president Barack Obama said he was "shocked and saddened" by Abe's death.
Abe and Mr Obama visited the site of Pearl Habour and Hiroshima in 2016 in an effort for the two countries to mend relations.
Mr Obama said he would "always remember the work we did to strengthen our alliance".
Former president Donald Trump said Abe was a "unifier like no other, but above all, he was a man who loved and cherished his magnificent country".
Vice President Kamala Harris, Secretary of State Antony Blinken and Defence Secretary Lloyd Austin also expressed their condolences to Abe.
"His killing is a tragedy for the people of Japan and for all those who value a free and open Indo-Pacific," Mr Austin said.
Speaking at a meeting of G20 foreign ministers in Bali, Mr Blinken called the assassination "shocking". Ms Harris said the US stands in solidarity with Japan in condemnation of the violence.