U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe began their meeting in Tokyo on Thursday by stressing a common message: their alliance is an asset not just for their two countries, but for the entire Asian-Pacific region.

Following a tete-a-tete over sushi Wednesday night, the two leaders met for a formal summit meeting Thursday morning to discuss a range of issues. Members of the press were invited to attend for the first 10 minutes, and the two leaders highlighted some of their security concerns in the region.

"The U.S.-Japan alliance is a foundation not only for our security in the Asia-Pacific region but also for the region as a whole," Mr. Obama said. "We are looking at a whole range of issues that are challenging at this time, including the threats posed by North Korea and the nuclearization that's been taking place in that country."

The meeting was held at the Akasaka Palace, a stately neo-baroque building near the imperial palace used as the government's official guest house. A dozen officials sat on each side of a long table under sparkling chandeliers. In contrast to Mr. Abe and his all-male team, Mr. Obama was flanked by two women. On his right was Caroline Kennedy, whom the president appointed as the U.S's first female ambassador to Japan last year. On his left was National Security Adviser Susan Rice.

Even as the Obama administration advances its "pivot" to Asia, it wants to see regional allies such as Japan and Australia take on bigger security responsibilities in a region rife with challenges, including China's military buildup and territorial disputes. That's because Washington faces mounting policy challenges elsewhere, from Ukraine to Syria, as well as constraints in its defense budget.

Mr. Abe, meanwhile, is eager to secure Mr. Obama's endorsement for his push to remove some of the tough constitutional restraints on Japan's military and allow it to play a greater role in the alliance and regional security.

"My administration intends to contribute to regional peace and prosperity more proactively than ever," he said. "Together with the United States, Japan would like to realize our leading role in the alliance in ensuring peaceful and prosperous Asia Pacific."

Mr. Abe commended Mr. Obama's four-nation tour of Asia Pacific as a "testament to the U.S.'s robust policy" of refocusing on the region.

Write to Yuka Hayashi at yuka.hayashi@wsj.com

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