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 February 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.
Asked to comment, the White House referred to the US State Department, which did not immediately respond