President Bush could hardly have picked a more critical time to host China's President Hu Jintao at the White House.
A flare-up in troubled waters between South Korea and Japan, faltering trilateral cooperation among the US, Japan, and South Korea, and the failure to persuade North Korea to come close to terms on its nuclear-weapons program all make China a pivotal player - while raising questions about US strength and influence in the region.
"The United States can play a more profound role in stabilizing the region," says Moon Jung In, international relations professor at Yonsei University in Seoul. "China may be happy to see what's happening."
While the United States tries to persuade China both to reduce its yawning trade surplus with the US and get North Korea to return to six-party talks, a potentially explosive quarrel between South Korea and Japan is frustrating Washington's efforts to join its two northeast Asian allies in common cause on the nuclear issue.
"High-ranking officials of the South Korean government have been talking about Korean-US cooperation rather than trilateral cooperation," says Kim Sung Han, director of North American studies at the Institute of Foreign Affairs and National Security, affiliated with South Korea's Foreign Ministry.
"Trilateral cooperation is vital to resolving the North Korean problem," he says.
The tendency in Korea is to blame Japan for somehow wishing to assert its own role in the region, reminding both Koreans and Chinese of the history of Japanese imperialism in Asia, culminating in the conquest of much of the Chinese mainland and 35 years of colonial rule over the Korean peninsula.
Memories of that history have leaped into the headlines as a result of a stand-off midway between Korea and Japan in what Koreans call the East Sea and the much of the rest of the world knows as the Sea of Japan.
The focal point is a cluster of 34 islets, basically uninhabitable, that both Korea and Japan claim as part of their national territory.
Korea calls the cluster "Dokdo," or "Solitary Island," while Japan calls it "Takeshima," or "Bamboo Island," and Japan also wants to give Japanese names to undersea rock formations surrounding the islands, basically volcanic rock thrust up from the sea.
The issue, simmering for years, reached a boiling point this week when Japan said it was sending two survey vessels to chart the waters around the islands, held by a garrison of Korean troops seen on Korean television manning anti-aircraft weapons and machine-guns as if to stave off enemy invasion.
Eager to prove his fearlessness in the face of the Japanese, South Korea's President Roh Moo-Hyun has ordered 18 patrol boats to form a blockade against the survey vessels.
"Some people are claiming territorial rights to former colonies that were once acquired through war and aggression," he told Christian leaders at a breakfast Thursday. Not just "good will," he said, as if preparing for war, but "wisdom and courage" were needed in such a crisis.
Shinzo Abe, Japanese government spokes-man, says the vessels are going there in defiance of a pledge of "stern action" by Korea's foreign minister, Ban Ki Moon, against any "provocation" by Japan.
Mr. Kim, of the Institute of Foreign Affairs and National Security, accuses Mr. Abe, an outspoken conservative who aspires to succeed Junichiro Koizumi as Japan's prime minister, of playing to the right-wing in refusing to address Korean sensitivities.
"Shinzo Abe has his own agenda," says Kim. "The Japanese are trying to increase their own role in the area of security. This is sending conflicting messages."
The sense here is that the US could rein in Japan but is reluctant to do so while cooperating closely with Japan on North Korea.
"The United States has been rather silent on these issues," says Kim Tae Hwan, research professor at Yonsei University. "Koreans have been very uncomfortable with the Japanese posture of aligning with the United States. Japan seems to disregard expectations from Korea."
While playing into the hands of China, the standoff over the islands also comes at an opportune moment in terms of South Korea's policy of rapprochement with North Korea.
South Korea's unification minister, Lee Jong Seok, goes to Pyongyang Friday for the first ministerial-level talks between North and South Korea in five months. He and his North Korean opposite number will have no trouble agreeing on the need to fend off what North Korea has already denounced as a "shameless" attempt at expansion.
It's a "very clear win-win" for both North and South Korea, says David Kang, a professor at Stanford University's Asia-Pacific Research Center. In the process, he says, the ruckus at sea "makes it look a lot as if Korea and China are cooperating more since they're both upset by Japan's moves."
Mr. Kang sees the standoff as "a distraction" that probably will not have "a fundamental effect on North-South Korean relations," but adds to the sense that six-party talks on North Korea's nuclear weapons are not likely to go anywhere.
"The US doesn't expect to make any progress on six-party talks," says Kang. "Nobody has a face-saving way out."