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President Obama said Thursday that he wants to see a dispute between China and Japan over islands in the East China Sea resolved peacefully, while affirming that America's mutual security treaty with Japan applies to the islands.

"Historically they have been administered by Japan and we do not believe that they should be subject to change unilaterally," Obama said at a news conference with Prime Minister Shinzo Abe. "What is a consistent part of the alliance is that the treaty covers all territories administered by Japan."

China and Japan have conflicting claims to the remote islands, called Senkaku by Japan and Diaoyu by China. The dispute has badly strained relations between the two Asian powers.

A U.S.-Japan defense treaty requires Washington to come to Japan's defense if it is attacked. Obama said his defense of that treaty is not a new position.

"The treaty between the U.S. and Japan preceded my birth, so obviously this isn't the red line that I'm drawing," the president said.

A Chinese government spokesman has said China has "indisputable sovereignty" over the islands and that "the so-called Japan-U.S. alliance" should not harm China's territorial rights.

Obama said he wants the maritime issue to be worked out "through dialogue." He urged the two sides to "keep the rhetoric low."

"It would be a profound mistake to continue to see escalation around this issue instead of dialogue," Obama said he told Abe during a private meeting.

While China is not on Obama's eight-day itinerary in Asia, leaders in Beijing are closely watching the president's tour. Obama's advisers insist that the trip -- and the White House's broader Asia policy -- is not designed to counter China's growing power, and they say the president is not asking Asian nations to choose between allegiance to Washington or Beijing. "We want to continue to encourage the peaceful rise of China," Obama said.

Abe said he and Obama agreed to cooperate on engagement with China, along with other topics, including a stalled trans-Pacific trade agreement and the impact of the U.S. military presence in Okinawa.

"The Japan-US alliance is more robust than ever before," Abe said.

On another Asian concern, Obama said he's not optimistic North Korea will change its behavior in the near future. But he said he's confident that by working with Japan, South Korea and others, the U.S. can apply more pressure so that "at some juncture they end up taking a different course."

"If in fact you are serious about North Korea being a normal nation then you've got to start changing your behavior," Obama said.

Obama added that China's participation in pushing North Korea is critical.

Obama's four-country visit to Asia is aimed at reaffirming his commitment to Asia even as the crisis in Ukraine demands U.S. attention and resources elsewhere. The ominous standoff between Ukraine and Russia threated to overshadow the trip as the president weighs whether to levy new economic sanctions on Moscow.

Obama began his day with a call on Emperor Akihito at the Imperial Palace, a lush, park-like complex surrounded by modern skyscrapers where he was greeted by a military honor guard and children holding U.S. and Japanese flags. After taking in the scene, the president, emperor and empress walked along a maze of red carpet into the palace for a private meeting, with U.S. Ambassador Caroline Kennedy and other aides trailing behind.

The president told the emperor that the last time they met, he did not have any gray hairs. "You have a very hard job," the emperor replied.

Obama opened the first state visit by an American president to Japan in nearly 20 years on Wednesday night, when he and Abe had dinner at Tokyo's famed sushi restaurant Sukiyabashi Jiro. Abe told reporters Obama praised the meal as "the best sushi he had had in his life."

Later Thursday, Obama planned to return to the Imperial Palace for a state dinner. He also planned to visit the Meiji Shrine, which honors the emperor whose reign saw Japan emerge from over two centuries of isolation to become a world power.

Obama's stops in Japan, South Korea, Malaysia and the Philippines serve as something of a do-over after he canceled a visit to Asia last fall because of the U.S. government shutdown. The cancellation provided fresh fodder for those in the region who worry that the White House's much-hyped pivot to Asia is continually taking a backseat to other foreign and domestic priorities.

"I think the president will want to make clear that this commitment will be unaffected by developments in Ukraine and other global events," said Jeffrey Bader, Obama's former Asia director. "Countries want to hear that the U.S. presence is in fact steady and strong as China rises."