Satellite images show North Korea is upgrading its only known nuclear reactor used to fuel its weapons program despite US bragging about the complete denuclearization of the Korean Peninsula.

The images, obtained by North Korea analysis outlet 38 North, indicate that North Korea is quickly progressing on several adjustments to the Yongbyon Nuclear Scientific Research Center.

The improvements include a new cooling water pump house, multiple new buildings, completed construction on a cooling water reservoir and an apparently active Radiochemical Laboratory. It is unclear whether the reactor is still in operation, the report said.

38 North notes that North Korean nuclear officials are expected to proceed with “business as usual” until Kim orders official changes to procedure.

These images come as US president Donald Trump and North Korean leader Kim Jong Un at the Singapore summit, the first meeting between a serving U.S. president and a North Korean leader signed an agreement that called for a denuclearized Korean peninsula.

In exchange for Kim’s promise to dismantle his nuclear weapons program, Trump has put on hold joint military drills with South Korea and Japan off the Korean Peninsula.

But Washington has made it clear that it won't lift tough economic sanctions against Pyongyang until its complete denuclearization.

Donald Trump claimed last week that North Korea was blowing up four of its big test sites and that a process of “total denuclearization ... has already started,” but officials like Secretary of Defense Jim Mattis said there was no such evidence.

Asked if North Korea had done anything toward denuclearization since the summit, U.S. Defense Secretary Jim Mattis told reporters: “No, I’m not aware of that ... obviously, it’s the very front end of a process. The detailed negotiations have not begun. I wouldn’t expect that at this point.”

Meanwhile Secretary of State Mike Pompeo says the United States stays committed to talks with North Korea but will “reassess” all ties if North Korea leader Kim Jong-un fails to deliver on denuclearization promises that he made to Donald Trump.