North Korea has restored part of a missile launch site it began to dismantle after pledging to do so in a first summit with U.S. President Donald Trump last year, South Korea's Yonhap News Agency and two U.S. think tanks reported on Tuesday.
Yonhap quoted lawmakers briefed by South Korea's National Intelligence Service (NIS) as saying that the work was taking place at the Tongchang-ri launch site and involved replacing a roof and a door at the facility.
Satellite images seen by 38 North, a Washington-based North Korea project, showed that structures on the launch pad had been rebuilt sometime between Feb. 16 and March 2, Jenny Town, managing editor at the project and an analyst at the Stimson Center think tank, told Reuters.
The Center for Strategic and International Studies released a report, also citing satellite imagery, that concluded North Korea is "pursuing a rapid rebuilding" at the site.
"Activity is evident at the vertical engine test stand and the launch pad's rail-mounted rocket transfer structure," the CSIS report said. "Significantly, the environmental shelters on the umbilical tower, which are normally closed, have been opened to show the launch pad."
The news comes days after a second summit on denuclearisation between Trump and North Korean leader Kim Jong Un broke down over differences on how far North Korea was willing to limit its nuclear programme and the degree of U.S. willingness to ease sanctions.
The summit took place in Hanoi on Feb. 27 and 28.
Trump told a news conference after an unprecedented first summit with Kim on June 12 in Singapore that the North Korean leader had promised that a major missile engine testing site would be destroyed very soon.
Trump did not identify the site, but a U.S. official subsequently told Reuters it was the Sohae Satellite Launching Ground, which is located at Tongchang-ri.
Asked to comment, the White House referred to the U.S. State Department, which did not immediately respond.
A U.S. government source said the NIS was considered reliable on such issues, but added that the work described did not seem particularly alarming, and certainly not on a scale of resuming missile tests that have been suspended since 2017.
Kim Jong Un also pledged at a summit with South Korean President Moon Jae-in in September to close Sohae and allow international experts to observe the dismantling of the missile engine-testing site and a launch pad.
Signs that North Korea had begun acting on its pledge to Trump were detected in July, when a Washington think tank said satellite images indicated work had begun at Sohae to dismantle a building used to assemble space-launch vehicles and a nearby rocket engine test stand used to develop liquid-fuel engines for ballistic missiles and space-launch vehicles.
However, subsequent images indicated North Korea had halted work to dismantle the missile engine test site in the first part of August.
The fact that the site had been dormant since August indicates the new activity is "deliberate and purposeful," the CSIS report said.
The breakdown of the summit in Hanoi last week has raised questions about the future of U.S.-North Korea dialogue.
U.S. Secretary of State Mike Pompeo said on Monday he was hopeful he would send a delegation to North Korea in the coming weeks but that he had "no commitment yet."
While North Korea's official media said last week Kim and Trump had decided at the summit to continue talks, its Vice Foreign Minister Choe Son Hui told reporters Kim "might lose his willingness to pursue a deal" and questioned the need to continue.
U.S. State Department spokesman Robert Palladino told a news briefing that the United States remains "in regular contact" with North Korea, but he declined to say whether they had been in contact since the summit.
Palladino said U.S. Special Representative for North Korea Stephen Biegun, who led pre-summit negotiation efforts, planned to meet his South Korean and Japanese counterparts on Wednesday.
Yonhap also quoted lawmakers briefed by intelligence officials as saying that the five-megawatt reactor at North Korea's main nuclear site at Yongbyon, which produces weapons-grade plutonium used to build bombs, had not been operational since late last year, concurring with a report from the U.N. atomic watchdog.
Yonhap quoted the sources as saying there had been no sign of reprocessing of plutonium from the reactor and that tunnels at North Korea's main nuclear test site in Punggye-ri had remained shut down and unattended since their widely publicized destruction in May, which Pyongyang said was proof of its commitment to ending nuclear testing.
The fate of the Yongbyon nuclear complex and its possible dismantling was a central issue in the Hanoi summit.