That's asking a lot, and it's not likely to go much beyond formal statements crafted in advance. Japan isn't giving way on such familiar issues as Korea's grip on Dokdo (the rocky islets that the Japanese call Takeshima), compensation to the Comfort Women, distorted textbook histories or disputes on trade. The Americans would dearly love for the Japanese and Koreans to join in military exercises, or at least to share intelligence, but these two U.S. allies are not on the same wavelength.
President Moon, when he calls on Biden, will go on about the depths of the U.S.-Korean relationship, but they'll be talking past each other. Moon prays that Kim Jong-un will invite him once more to Pyongyang to talk about all the good things North and South Korea can do for one another, but Kim won't be happy until Moon shows clear signs of doing away with South Korea's alliance with the U.S. For Kim to be happy, Moon needs to halt military exercises with the U.S., even the computer simulations of operations. It's not enough for the Americans and South Koreans to have agreed on no troops running around the countryside. They have to stop the computer games too.
The Japanese take quite a different view. They see no prospect of reconciliation, and they think the only way to deal with the North is to get tough. That means keeping or increasing sanctions, demanding the safe return of Japanese kidnapped years ago from the beaches in Japan, and getting the U.S. to stick to an equally hardline position.
Most immediately, the Japanese are fearful that the Chinese will escalate their intimidation campaign in the waters surrounding the Senkaku Islands, out there in the East China Sea north of Taiwan. The breakaway regime of Taiwan also claims the Senkaku, which the Chinese call Diaoyu, but Taiwan fears that sooner or later, China's President Xi Jinping will decide that the time for empty threats is over and take Taiwan by force.
All of this tension in the region gives Biden and Suga much to talk about. Biden will assure Suga that the Senkaku problem falls within the U.S commitment to defend Japan, and they both will agree totally on the need for North Korea to get rid of its nukes and stop developing missiles capable of flying warheads to distant targets. The Japanese aren't worried about intercontinental ballistic missiles. It's the mid-range ones, within range of their own turf, that bother them.
Too bad for the U.S. vision of trilateral cooperation that Moon doesn't share a common cause with the Americans on either Japan or China. Quite aside from all the issues that never get settled, such as Dokdo-Takeshima and the Comfort Women, he would like to get along great with China, which he believes can hold Kim in-line and maybe convince him to return to talks. Moon is not going to side with Japan on the Senkaku dispute any more than he's sticking up for Taiwan, which the U.S. also is committed to defend.
The Americans, working to keep up appearances with both Japan and Korea, are forever repeating the cliche that there's "no daylight between us," meaning that they're so close to both countries that they're almost hugging ― just not at the same time.
That's not to say that Moon won't agree ― yes yes, nukes are bad and North Korea should get rid of them. He'll sign on to denuclearization but with considerably less emphasis than Suga. For Moon, the best hope is for the U.S. to agree step-by-step on the removal of sanctions in return for the usual pledges of North Korean denuclearization.
It's a tale told over and over, and we're going to hear it all again when first Suga and then Moon pay their respects at the White House.
Donald Kirk (www.donaldkirk.com) has been covering the nuclear standoff for decades.