(CNN) Kim Jong Un shocked the world in 2018 by transforming his image from nuclear-armed tyrant to global statesman.

So what does he have up his sleeve for 2019?

Analysts believe that key clues will emerge during his annual New Year's Day speech -- essentially North Korea's version of the State of the Union in the United States.

Experts will be watching for any mention of a second summit with US President Donald Trump or anything on Pyongyang's nuclear weapons program. Kim could also reveal key decisions on economic policy and inter-Korean relations.

In a sign of his new diplomatic push, Kim sent a letter to South Korean President Moon Jae-in on Sunday. In it, Kim said he regretted not being able to visit Seoul in 2018 but expressed a strong will to travel to the South Korean capital in the future.

Few expect Kim to rock the boat dramatically in Tuesday's speech. Many believe the young leader holds some of the best cards of all the geopolitical players with a stake in the future of the Korean Peninsula. Most do not expect Kim to risk his standing in a speech that's largely intended for a domestic audience.

"He's got the United States and South Korea where they want them right now," said Evans Revere, a former US assistant secretary of state for East Asian and Pacific Affairs and current senior director with the Albright Stonebridge Group.

North Korea's diplomatic achievements in 2018 would have been unthinkable a year earlier. In the lead up to Kim's 2018 New Year's speech, Pyongyang had tested its most advanced long-range missile to date and its most powerful nuclear bomb, after months of similar weapons tests and saber-rattling between North Korea and the US.

Few would have predicted that the following year, Kim would meet Moon three times, leave his country for the first time since taking power in 2011 and become the first North Korean leader to sit face to face with a sitting US President.

JUST WATCHED South Korean train heads North for first time in decade Replay More Videos ... MUST WATCH South Korean train heads North for first time in decade 01:13

That dramatic shift began with the New Year's address. Kim spoke warmly of the importance of inter-Korean relations, and wished his South Korean compatriots well in hosting the Pyeongchang Winter Olympics. Moon would go on to seize Kim's olive branch as an opportunity to jumpstart cross-border relations.

"It was a seminal, critical and central document in terms of understanding North Korea's game plan and North Korea's intentions," Revere said.

"I've never seen a game plan more transparently laid out than it was laid out in that speech."

Nuclear weapons

Kim kicked off the last two years with speeches that broke news, revealed major policy decisions and dropped rhetorical hints as to what the rest of the world should expect from his country in the coming year.

In 2017 he used the speech to say his country was close to testing an intercontinental ballistic missile (ICBM) -- the type necessary to delivery a nuclear weapon to the continental US. Pyongyang went on to test three ICBMs that year.

JUST WATCHED Kim Jong Un's 2018 New Year's address Replay More Videos ... MUST WATCH Kim Jong Un's 2018 New Year's address 02:20

The young leader opened 2018 by offering to send a delegation to the Winter Olympics in Pyeongchang, but also pledging to mass-produce nuclear weapons and ballistic missiles and warning Washington that the nuclear launch bunch was "always on the desk in my office."

Recent reports from open-source intelligence analysts appear to confirm that North Korea has not stopped working on its weapons program, though Kim has kept his promise not to test-fire missiles or nuclear bombs.

Though continued work on these weapons may violate the spirit of Trump and Kim's summit in Singapore, the North did not commit itself to halting all work on its nuclear program in 2018. The two leaders agreed to start rebuilding the bilateral relationship and bring peace to the Korean Peninsula. In terms of nuclear weapons, North Korea committed "to work toward complete denuclearization of the Korean Peninsula," a vague term that experts say Washington and Pyongyang interpret differently.

JUST WATCHED North Korea expert says nuclear threat remains Replay More Videos ... MUST WATCH North Korea expert says nuclear threat remains 11:43

Critics accuse the Trump administration of failing to get Pyongyang to sign on to anything specific. North Korea has not agreed to any timeline to give up its nuclear weapons and ballistic missiles, nor has it committed itself to declaring its weaponry and key weapons facilities -- steps that experts say are crucial in any disarmament talks.

Experts will be watching for any mention of the nuclear program in next year's speech, especially if it strikes the defiant tone of this year's address -- when Kim declared that "no force and nothing" could reverse the gains his country had made in nuclear weapons development.

"He said that this January, but he's engaged in this diplomatic process with the US," said Duyeon Kim, a adjunct fellow at the Center for New American Security.

"It'll be interesting to see how Pyongyang negotiates going forward because Kim Jong Un claimed this year that nobody could reverse their nuclear capabilities."

Economics

Clues about what Pyongyang sees as the speech's key passages often come in the form of rhetorical devices, such as when Kim switches to a first-person voice, according to John Delury, a professor at Yonsei University's Graduate School of International Affairs in Seoul.

Delury said he'll watch closely for comments about the country's economic development, something likely to be highly scrutinized inside North Korea and which could prove to be the most important part of the speech.

In the 2018 speech, Kim acknowledged that the moribund economy was in need of a boost and committed himself to improving it. However North Korea does not make its economic statistics available internationally, making it difficult to precisely track its economic performance and determine what proportion of its population works in more modern fields.

Just days before his first summit with Moon in April , Kim took the drastic step of declaring that North Korea had successfully completed its nuclear weapons program and would suspend nuclear and missile tests. It would now solely focus on effort to "dramatically raise people's lives" by developing a "strong socialist economy."

The two-pronged strategy of nuclear and economic development, known as "byungjin," had been in place since shortly after Kim took the reins from his father in 2011. Abandoning it represented a significant policy shift.

However, the regime has yet to articulate a coherent vision or plan with respect to development.

"There's some pressure in this year's New Year's speech to articulate a vision of a real focus on economic development," Delury said.

"How does Kim Jong Un reflect this strategic shift to economic development?"

In recent months, North Korean state media has focused heavily on economic issues, often touting the importance that people inside the country work vigorously to increase production.

But that hardly constitutes a plan. Investors see North Korea as a land ripe with opportunities, and they're looking for a strategy that would allow for infrastructure investments connecting South Korea to Russia by rail or opening up North Korea's relatively well-educated, low-wage workforce to manufacturers from the region.

All of that, however, is off-limits at the moment due to the sanctions levied on Pyongyang as punishment for its nuclear weapons program.

And Delury says it's unlikely for Kim to come out and just announce a detailed strategic shift. As is everything with North Korea, the devil will be in the details.

"I wouldn't expect a kind of revolutionary statement of a new economic concept, but you kind of have to look within their language for what are progressive ideas by North Korean standards," Delury said.