U.S. Vice President Joe Biden, in a meeting here with South Korean President Park Geun Hye on Friday, called for an improvement in relations between South Korea and Japan, according to South Korea's presidential office.
"Vice President Biden said he hopes stumbling elements for relations between South Korea and Japan will be cleared as soon as possible and that relations become smooth," a statement from the office said.
Biden said both Japan and South Korea are key allies of the United States.
In response, Park said she expects "sincere measures" from Japan while she "hopes to build up a future-oriented relationship with Japan based on trust."
Relations between Japan and South Korea are strained over a territorial dispute in the Sea of Japan and issues that stem from Japan's 1910-1945 colonial rule of the Korean Peninsula and its wartime aggression in Asia.
Seoul has strongly objected to remarks by Japanese lawmakers apparently justifying their country's militaristic past.
Those issues have prevented Japanese Prime Minister Shinzo Abe and Park from holding a summit since Park took office in February.
As for China's new, controversial air defense zone, Park explained to Biden South Korea's position, and Biden "evaluated Park's explanation and South Korea's efforts," the statement said without further elaboration.
"The two sides agreed to hold close consultations on the issue," the statement said.
China's establishment of the air defense zone late last month sparked a strong reaction in Seoul as it overlaps South Korea's.
At the outset of the talks, Park told Biden in the presence of reporters, "The Korea-U.S. alliance is the linchpin to stability and security not just on the Korean Peninsula but in Northeast Asia."
Biden stressed that U.S. President Barack Obama made a strategic decision at the outset of his administration to increase focus on the Asia-Pacific region and "rebalance" U.S. engagements, activities, and resources toward and within the Pacific basin.
"I want to make one thing absolutely clear: President Obama's decision to rebalance to the Pacific basic is not in question," he said.
"The United States never says anything it does not do," he said, cautioning doubters that it has "never been a good bet to bet against America" and adding that "America will continue to place its bet on South Korea."
Biden arrived in South Korea on Thursday for a three-day visit on the final leg of his three-nation trip this week which took him first to Japan and then China.
Following his meeting with Park, Biden delivered a speech on U.S.-South Korea relations and U.S. policy toward the Asia-Pacific at Yonsei University in Seoul.
In his speech, Biden reiterated that the United States does not recognize China's new air defense zone.
"I was absolutely clear on behalf of my president: We do not recognize the zone. It will have no effect on American operations. None. Zero," Biden said, referring to discussions he held in Beijing earlier in the week.
In the speech, he also reconfirmed that the United States will not allow North Korea to continue its nuclear weapons program.
"The U.S. will not accept and tolerate a nuclear-armed North Korea," Biden said.
On Saturday, he will participate in a wreath-laying ceremony at a war memorial and visit the Demilitarized Zone that separates North and South Korea.