It may be one of the last countries to let travelers in — and it's not China

In 2008, the national anthems of both North Korea and the United States resonated throughout the East Pyongyang Grand Theatre — echoing hopes of a thawing relationship between the countries.

The curtains have since long closed on these hopes.

The historic concert, performed by the New York Philharmonic is one of Mark Edward Harris' favorite moments of his 10 trips to the "Hermit Kingdom."

Harris, a Los Angeles-based photographer, told CNBC that he hopes to return to North Korea soon. 

Covid holdouts in Asia — such as Japan and Hong Kong — have relaxed border restrictions, but North Korea is expected to keep its rules firmly in place.

Furthermore, North Korea's reopening depends on two countries — China and Russia. Travelers eager to visit it often have to enter through them.

Even if North Korea were to open tomorrow, "neither option is available," said Simon Cockerell, general manager of Koryo Tours, which specializes in North Korean tourism. He cited the ongoing conflict between Russia and Ukraine and China's strict border closures.

North Korean's border reopening "entirely relies" on how China reopens to foreign travelers, said Rowan Beard, a tour manager at Young Pioneer Tours.

"The majority of tourists going to North Korea go directly through China," he said.

If China does not issue tourist visas or allow tourists to transit through it, it will be impossible for Westerners based in China to go to Pyongyang, agreed Rayco Vega, general manager of tour agency KTG Tours.

Even as North Korea retreated into its shell during the pandemic, demand to visit never waned, according to several tour agencies.

"There has always been solid demand, and it may even be pent up at this point,"  said Cockerell.

North Korea tours make up more than 90% of Koryo's revenue stream, he said.

Beard agreed, saying travelers still send requests to visit North Korea.

"I receive emails daily from those asking if North Korea has reopened and if they can go," he said. "They're on the waiting list, and once it does reopen, it's first-come, first-served."

North Korea's tourism revenue rose around 400% between 2014 and 2019, according to the North Korea analysis database 38 North.

Tours into North Korea comprised about 75% of his company's business before the pandemic, said Beard. He organized trips for about 1,200 tourists in 2019, comprising mainly Australians, Brits, Canadians, the Dutch and Germans, he said.

"We could have taken more but the demand for travel to North Korea was also in high demand with the Chinese market, which made flight and train tickets incredibly limited," he said.

With China still adhering to its zero-Covid strategy, the tour agencies that spoke to CNBC estimate that North Korea may reopen to foreign tourists in 2024 — or later.

"Our guess is that the DPRK will be one of the last countries to let travelers in," said Vega.

"They will take the most conservative line on this," Cockerell said. "The country has also closed for months due to SARS in 2003 and Ebola in 2015, so they do act decisively in the face of pandemics."

He added that a "a European-style relaxed attitude" toward travelers won't come anytime soon, and expects strict controls to remain in place even when it does reopen.

Beard said he believes North Korea's reopening will be a "tedious" one, plagued by Covid testing, tracking apps and face mask rules, even when the "rest of the world will have mostly moved on."