WASHINGTON, March 6, (RTRS): North Korea has restored part of a rocket test site it began to dismantle after pledging to do so in a first summit with US President Donald Trump last year, while Trump’s national security advisor warned that new sanctions could be introduced if Pyongyang did not scrap its nuclear weapons program.

South Korea’s Yonhap News Agency and two US think tanks reported on Tuesday that work was underway at the Sohae Satellite Launching Station at Tongchang-ri, even as Trump met with North Korean leader Kim Jong Un at a second summit in Hanoi last week. That summit broke down over differences on how far North Korea was willing to limit its nuclear program and the degree of US willingness to ease sanctions. Trump’s national security adviser, John Bolton, told Fox Business Network on Tuesday that following the Hanoi summit, Washington would see whether Pyongyang was committed to giving up its “nuclear weapons program and everything associated with it.”

“If they’re not willing to do it, then I think President Trump has been very clear … they’re not going to get relief from the crushing economic sanctions that have been imposed on them and we’ll look at ramping those sanctions up in fact,” said Bolton, a hardliner who has advocated a tough approach to North Korea in the past. Separately, two US senators sought to dial up pressure on North Korea by reintroducing a bill on Tuesday to impose sanctions on any bank that does business with its government. US Secretary of State Mike Pompeo said on Monday he was hopeful the United States would send a delegation to North Korea in the coming weeks, but Bolton’s remarks and the apparent developments at the Sohae test site may cause new challenges for diplomats hoping to restart negotiations after the failed summit.

Satellite images seen by 38 North, a Washington-based North Korea project, showed that structures on the Sohae 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.”

Asked to comment, the White House referred to the US State Department, which did not immediately respond. A US government source said the South Korean intelligence agency cited by Yonhap 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. Analysts cautioned that the site has never been used to launch an intercontinental ballistic missile and there is no evidence to suggest a test is imminent, but the site has been used to test missile engines and past satellite launches have helped scuttle talks with the United States.

Kim Jong Un 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 enginetesting 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.