WASHINGTON - US President Barack Obama is certain to heap praise on South Korea and Japan as he attends back-to-back summits but some experts see a subtle shift as he views Seoul as the more dynamic ally.
In separate remarks this year that made diplomats run to their thesauruses, Obama called South Korea "the linchpin" of regional security and Japan "one of the cornerstones" of security throughout the world.
The distinction may seem academic but it has quietly concerned some Japanese policymakers who have long viewed their country as, well, the linchpin of US strategy in Asia.
Bruce Klingner, a senior research fellow at the Heritage Foundation, said he has spoken with US officials who described Obama's "linchpin" remark -- made when he met South Korean President Lee Myung-Bak in June in Canada -- as a deliberate, if nuanced, sign of the administration's views.
Lee has been a steadfast US ally, coordinating moves in a standoff with communist North Korea. It is a striking change from Lee's liberal predecessor Roh Moo-Hyun, who openly criticized US troops and US policy toward the North.
In Japan, the center-left Democratic Party of Japan (DPJ) last year ended decades of conservative rule and initially tried to win more concessions on a deal to move a controversial US air base on Okinawa island.
"Certainly under Lee Myung-Bak you have an administration that's far more forward-looking to transform the alliance into having broader responsibilities," Klingner said.
"Compare that with the DPJ government in Tokyo, which came into office downplaying the importance of the alliance and seeking a relationship that was more equidistant between Washington and Beijing," he said.
US-Japan relations have improved since Naoto Kan took over as prime minister in June and the two nations have pulled together amid a showdown between Tokyo and Beijing over disputed islands.
But experts still see a gap in momentum in US relations with Japan and South Korea. The Obama administration is racing to complete a free trade agreement with South Korea by the time he arrives Wednesday for the summit of the Group of 20 major economies in Seoul.
Obama heads on Saturday for a summit of the Asia-Pacific Economic Cooperation forum in Yokohama, after which he will visit the giant Buddha statue in nearby Kamakura.
The relationship with South Korea "has been the one real bright spot in US policy toward Asia," said Weston Konishi, associate director of Asia-Pacific studies at the Institute for Foreign Policy Analysis.
"You have to give President Lee some credit for having the kind of leadership skills and vision that would allow for an expanded partnership, whereas we don't see that impetus in Tokyo," he said.
William Grimes, founding director of Boston University's Center for the Study of Asia, said that South Korea has succeeded in "punching over its weight" by hosting the Group of 20 summit and winning the appointment of its former foreign minister Ban Ki-moon as the UN secretary general.
But Grimes cautioned not to discount Japan, whose population is more than double South Korea's. Japan remains the world's third largest economy and its makers of cars and electronics are household names around the world.
Japan plays an active role in global economic policy and has far outpaced most countries as a donor on issues ranging from development to climate change. Japan has committed 2.35 billion dollars for Afghanistan since 2001.
Grimes said that Japan is often less visible on major international issues due to its low-key style, with bureaucrats focused on "nuts and bolts" on the ground.
"South Korea has done a really nice job of trying to leverage its position of not being Japan or China," Grimes said. "But I don't think that Korea has the same opportunities (as Japan) because of the size of the country and the global impact of Korean companies."
"Japan is a big global player. It's just not an obvious global player," he said.