BEIJING — China reacted with strong displeasure on Saturday to a promise by Defense Secretary Jim Mattis that the United States would defend two uninhabited islands in the East China Sea that Japan controls but China also claims as its own.
Mr. Mattis, the first member of President Trump’s cabinet to visit East Asia, had told Japanese officials earlier Saturday that America’s defense obligations to Japan extended to the disputed rocky outposts, known in China as the Diaoyu and in Japan as the Senkaku.
The chief spokesman for China’s Foreign Ministry, Lu Kang, accused Mr. Mattis of putting regional stability at risk and urged him to forgo what he called a Cold War mentality.
“We urge the U. S. side to take a responsible attitude, stop making wrong remarks on the issue involving the Diaoyu islands’ sovereignty, and avoid making the issue more complicated and bringing instability to the regional situation,” Mr. Lu said in a statement posted on the ministry’s website.
He described the 1960 defense treaty between the United States and Japan, which Mr. Mattis cited in pledging to defend the islands, as a “product of the Cold War, which should not impair China’s territorial sovereignty and legitimate rights.”
Mr. Mattis was not staking out a new American position; while in office, President Barack Obama said that the United States would defend the islands.
But the defense secretary’s words were reassuring to Japanese officials, who had been unnerved by Mr. Trump’s remarks as a presidential candidate suggesting that he might reduce America’s military commitments to its Asian allies.
The disputed islands have been among a number of potential points of contention as China builds up its presence in the East and South China Seas.
Chinese and Japanese vessels regularly maneuver at close quarters in the waters as China tries to challenge Japan’s control of the islands.
Last year, China sent a warship to within 24 miles of the islands. President Xi Jinping of China declared much of the East China Sea to be a Chinese air defense zone in 2013, and since then China has regularly sent fighter jets to patrol the area.
At a news conference in Tokyo , Mr. Mattis cited Article 5 of the United States-Japan treaty, which commits the United States to defend Japan or territories that it administers against attack.
