Japan's Prime Minister Shinzo Abe, left, and China's President Xi Jinping, right, shake hands during their meeting at the Great Hall of the People, on the sidelines of the Asia-Pacific Economic Cooperation (APEC) summit, in Beijing, Monday, Nov. 10, 2014. (Kim Kyung-Hoon/AP)

CHINA’S XI Jinping and Japan’s Shinzo Abe were careful not to smile when they met in Beijing on Monday — the first encounter between the leaders of Asia’s two biggest powers since either took office. Their 25-minute get-together nevertheless represented a welcome step toward easing tensions in East Asia. At the beginning of the year, the two nations were embroiled in a deepening conflict over a string of tiny islands, exacerbated by the expansive foreign policy ambitions of both leaders. While neither the dispute nor the conflicting agendas have been resolved, the dangerous downward spiral of Japanese-Chinese relations has at least been arrested.

For that, credit mostly goes to Mr. Abe, who played suitor to Mr. Xi in seeking a meeting at the Asian summit meeting in Beijing. The Japanese leader has rankled leaders and public opinion around the region with nationalist rhetoric and gestures such as a visit to a Tokyo shrine where war criminals are among those honored. But Mr. Abe’s government has mostly been on the defensive in the dispute over the Senkaku (or Diaoyu) Islands, which have long been under Japan’s control but have been the target of increasingly assertive claims — and naval incursions — by China.

Mr. Xi, who during his first two years in power has overseen a disturbing series of aggressive acts toward other countries in the South China Sea, has played on easily roused public hostility toward Japan. While ostentatiously refusing to meet Mr. Abe, the Chinese president set a couple of tough conditions for reversing himself: that Japan acknowledge that the sovereignty of the islands was disputed and that Mr. Abe pledge not to return to the Yasukuni shrine. In the end both issues were finessed. Mr. Abe made no public promise but dispatched emissaries who privately assured Beijing he planned no future Yasukuni visits, and the two governments agreed on a statement saying they had “different positions” on the islands.

The fragile accord is a help to President Obama, who has been hoping to build closer ties to Mr. Xi even while supporting U.S. allies — including the Philippines as well as Japan — that are resisting China’s exaggerated territorial claims. Mr. Obama usefully made it clear this year that the United States would come to Japan’s defense in the event of an attack on its forces around the islands, but he also pressed Mr. Abe to avoid further nationalist gestures. Asian fears that China might be emboldened by Mr. Obama’s reluctance to use U.S. hard power in Syria or Ukraine, voiced by numerous official visitors to Washington, have not borne out.

That leaves unanswered whether the Sino-Japanese summit reflects a stepping back by Mr. Xi from the aggressive foreign policy of his first two years. With his power in Beijing apparently consolidated, and myriad domestic problems to address, that would be a logical tactical step for a ruler with eight years left in his prospective tenure. Mr. Xi’s scowl as he shook Mr. Abe’s hand did not seem to foreshadow detente, but Mr. Abe expressed optimism Tuesday that Japan and China would “return to our basic focus of mutually beneficial and strategic relations.” We hope China shares that goal.