SEOUL, June 7 (UPI) -- Operations are continuing at a North Korean uranium enrichment site, said analysts for website 38 North, a project of Washington, D.C.-based think tank The Stimson Center.
According to an examination of recent commercial satellite imagery of North Korea's Yongbyon Nuclear Scientific Research Center, "operations at the Uranium Enrichment Plant (UEP) remain ongoing," the report published Wednesday stated.
The report noted that activity at the site includes vehicles, equipment and personnel arriving and departing, including a tanker trailer leaving a large cylinder or shipping container near the facility's gas centrifuge hall.
The images appear consistent with a liquid nitrogen tanker trailer, the analysts wrote, which is a necessary component in the uranium enrichment process.
"Our observation, that periodic material transport (e.g., possibly to deliver liquid nitrogen) has continued at the Uranium Enrichment Complex over time, provides a new indicator that the complex is operational, and therefore that it is also most likely producing enriched uranium," the report states.
The analysis, based on imagery from the months leading up to May 28, could not determine the actual levels of enrichment or the total production throughput of the facility's roughly 4,000 centrifuges.
North Korea has built nuclear weapons using both plutonium and uranium as fissile materials.
The report comes as negotiations between Washington and Pyongyang over the North's nuclear program remain at a stalemate.
North Korea has been looking for relief of some international sanctions during a gradual process of winding down its nuclear program, but the United States has continued to hold out for complete denuclearization first.
At a second U.S.-North Korea summit held in Hanoi, Vietnam, in February, North Korean leader Kim Jong Un offered to dismantle the Yongbyon complex in exchange for the easing of sanctions, but the summit ended abruptly without any deal.
Earlier this week, North Korea indicated that its patience was wearing thin over the stalled negotiations.
"The U.S. would be well-advised to change its current method of calculation," an unnamed spokesman for North Korea's ministry of foreign affairs said in a statement carried by state-run Korean Central News Agency.
"There is a limit to our patience," he added.
Tensions between North Korea and the United States have risen since the February summit, as North Korea launched what the Pentagon said were short-range ballistic missiles on May 4 and May 9, the first such launches since late 2017.
Last month, Washington announced that it had seized a North Korean cargo ship on suspicion that it violated sanctions. Earlier this week, the U.S. Seventh Fleet deployed a Coast Guard ship in the Yellow Sea in waters near North Korea, a move seen by some as an effort to step up monitoring and enforcement of sanctions.
However, President Donald Trump on Wednesday maintained an optimistic take on the U.S.-North Korea relationship.
"It's been going pretty well because there hasn't been testing of anything major, and, frankly, there's been no nuclear testing in a long period of time," he told reporters during his visit to Ireland.
"I think that Chairman Kim would like to make a deal, and I'd like to make a deal with him. I look forward to seeing him in the appropriate time," the president added.