VLADIVOSTOK, Russia - US Secretary of State Hillary Clinton arrived late Friday for an Asia-Pacific summit seeking progress in the tense South China Sea, but with concerns about frayed ties between Japan and South Korea.
Clinton, filling in for President Barack Obama as he enters the home stretch of his re-election campaign, will also discuss easing the diplomatic stalemate over Syria's bloodshed during talks with host nation Russia.
US officials said Clinton planned to meet at the Asia-Pacific Economic Cooperation summit in Vladivostok with the leaders of Japan and South Korea -- US allies whose relations have dramatically soured in recent weeks.
The two leaders, Japanese Prime Minister Yoshihiko Noda and South Korean President Lee Myung-Bak, do not plan to meet each other during the summit as nationalist passions flare over islands disputed between the two nations.
The Obama administration, which has put a renewed focus on Asia, had hoped that Japan and South Korea would overcome deep historical animosity to work together on shared issues such as China's rise and nuclear-armed North Korea.
But a senior US official travelling with Clinton did not predict a breakthrough between the two countries in Vladivostok.
"This is a matter for Japan and South Korea. We encourage dialogue in each of our bilateral interactions with them," the official said on Clinton's plane under customary condition of anonymity.
"We've underscored that the positive relationship between Japan and South Korea is in the strategic best interest of the United States and we will continue to do so," the official said.
Just a few months ago, Japan and South Korea were on the verge of signing a landmark intelligence-sharing pact. But Lee, long seen as a top ally of Obama, faced a backlash at home and made an unprecedented trip to islands known as Dokdo in Korean and Takeshima in Japanese.
The issue flared up as the United States was putting more diplomatic energy into separate disputes in the South China Sea, where Vietnam and the Philippines have accused Beijing of a campaign of intimidation to exert its own claims.
In Vladivostok, Clinton plans to meet with the leaders of Malaysia, Singapore, Thailand and Vietnam, underscoring her interest in the South China Sea, after stops this week in China, Indonesia and Brunei.
Clinton, who has become the first US secretary of state to visit all 10 members of the Association of Southeast Asian Nations, is hoping that the bloc and China will agree to a code of conduct to manage maritime disputes.
On relations with China Clinton told reporters Thursday that the United States and "certainly I, am not going to shy away from standing up for our strategic interests, and in expressing clearly where we differ".
"The mark of a mature relationship -- whether it's between nations or between people -- is not whether we agree on everything, because that is highly unlikely between nations and people, but whether we can work through the issues that are difficult," she added.
Clinton plans to meet Saturday morning with Russian Foreign Minister Sergei Lavrov for talks expected to focus on deep disagreements between the two nations on the bloodshed in Syria.
Russia is the main diplomatic and military supporter of President Bashar al-Assad, who has led a clampdown that activists say has killed more than 26,000 people, and has vetoed with China two UN draft resolutions on Syria.
Russia said that President Vladimir Putin will meet only briefly with Clinton as she is not a head of state.
Putin skipped a Group of Eight summit in the United States in apparent anger over Obama not taking time out of his re-election campaign to make the trip to the Russian far east.
A US official was unfussed about Putin's plans with Clinton, saying: "I think this is exactly what the two sides had planned and what we expected given that she's sitting in for the president."