(CNN) Another "beautiful letter" for President Donald Trump arrived this week from Kim Jong Un -- the first since the utter collapse of the last summit in February between the two leaders in Hanoi.

Though the letter was said to have been thin on any real substance, and lacking a path to a way forward, behind the scenes, it seems, all is not thoroughly lost. As long as nations are talking, it is unlikely that missiles will be exchanged.

Still, talks can take many paths. Kim's letter to Trump was followed quickly by reports from Beijing that Chinese President Xi Jinping will be paying his first visit to Kim on Thursday and Friday. Effectively, Xi will be injecting himself directly in the path of Trump's efforts to build a unique relationship with Kim, and barely a week before Trump next encounters Xi at the G-20 summit in Osaka, Japan. Trump does not like being upstaged on the world stage.

But although contact between Korea and the United States has never been easy, the office of the US Special Representative for North Korea under Stephen E. Biegun , a veteran foreign policy specialist and Ford Motor Co. executive, continues to function on a number of levels.

However, the United States has no diplomatic representation in Pyongyang -- although 24 countries do have full embassies there, including Britain, Germany and Sweden , which has long looked after American interests there.

There is not even a formal "American interests section" there, meaning no US diplomat has the right to stay in Pyongyang.

When you consider these roadblocks, it may look like negotiations are at a complete standstill.

But during this period of what can best be described as a hiatus after the collapse of talks in Hanoi, there are four principal tracks that seem to be ongoing in one fashion or another -- some more desultorily than others.

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First is the question of diplomatic representation. The closest direct contact between the two nations is at the United Nations in New York where North Korea does maintain a fully-staffed mission. But these diplomats cannot open their mouths without strict instructions from their government -- a reality that stretches back to the days of Kim Jong Un's grandfather a half century ago. So the warming of relations to the point of each country at least maintaining an "interest section" in each others' capitals -- much as the United States maintained for 38 years in Havana -- would be a first important step. It took 16 years, from the time the US severed diplomatic relations with Cuba's communist regime in 1961, for an interest section to open under Swiss auspices in 1977. This continued until a full embassy opened in 2015 when, under Barack Obama, the United States restored full diplomatic relations. So the case with North Korea is hardly unique; nor is it impossible to envision a change.

Allied with this is an improvement in "atmospherics" between the two countries. This could include people-to-people exchanges and could be some first steps toward warming of diplomatic relations. Also not unprecedented. In 2008, the New York Philharmonic performed in Pyongyang's Grand Eastern Theater under conductor Lorin Maazel and conducted master classes for North Korean musicians.

Then there is the question of a peace treaty between the two countries. The end of the Korean War in 1953 has still only been marked by an armistice that established a neutral or demilitarized zone 148 miles long and 2.5 miles wide that meanders, strewn with mines and military guard posts, more or less along the 38th parallel.

peace treaty has been raised by Kim as important to him, and there is no real reason that could not be a suitable carrot that might lead to further, more substantive progress.

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A third agenda item is the one that has been most fully satisfied and that both Trump and Biegun point to with pride as a precedent-setting symbol of progress.

At the Hanoi summit, there was actual progress on the first three issues, some of which, I'm told, reached the point of written documentation. But all of these died with the collapse of the leaders' talks with respect to the fourth and most intractable issue -- the denuclearization of North Korea. Pyongyang has framed this with respect to the US first removing its nuclear threat in all of the Korean peninsula, though the United States maintains no nuclear weapons in the South. The number of such weapons peaked at 950 in 1967; the final warhead was withdrawn in 1991.

Some negotiators have suggested to me that this issue can only really be decided on a leader-to-leader basis. Which would seem to mandate that much higher-level talks be resumed, in some fashion, than has been the case since the collapse of the Hanoi summit. Secretary of State Mike Pompeo will be visiting the two other nations with major stakes -- South Korea and Japan -- later this month. But Kim has said publicly he is no longer interested in negotiating with Pompeo, branding him as not sufficiently "mature."

Since then, Kim has met directly with Russian President Vladimir Putin in Vladivostok -- Putin journeying from Moscow across seven time zones to accommodate Kim's preference to travel by train. The two leaders agreed, Putin said, that the world needs "international law, not law of the fist," before flying off to Beijing to brief Chinese leader Xi Jinping.

Part of the delay in any further progress may be the fact that North Korea finds it difficult to take on more than one issue at a time. Since the Hanoi breakdown, Pyongyang has held a national election, with one political party, for a new parliament, and named a new State Affairs Commission , the nation's ruling body, similar to the Soviet Politburo.

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Still, there are some very thin positive signs, beyond the beautiful letter sent to President Trump. On Wednesday, Kim sent his sister, Kim Yo Jong , to the border with South Korea to hand-deliver a note to the South's national security advisor, Chung Eui-yong. It expressed the Kims' condolences on the death of a former South Korean first lady, Lee Hee-ho, who had visited the North several times and whose husband had encouraged the "sunshine policy" of reconciliation and economic development between the two Koreas.

Such "green shoots" need desperately to be encouraged between Washington and Pyongyang. Meanwhile, it is essential that Biegun and his deputies keep both allies and interested parties -- particularly Russia and China -- as well informed as Kim seems to be doing on his end.