Nuclear-armed North Korea is preparing for a large-scale military parade to mark its Foundation Day next month, researchers said Friday, the same day the White House canceled a trip by the top U.S. diplomat to Pyongyang.

The 38 North monitoring group said that satellite imagery taken Wednesday of the Mirim Parade Training Ground showed approximately 120 military vehicles in formation practicing on the facility’s roads. These included what may be six tarp-covered Scud-class transporter-erector-launchers (TELs), as well as unmanned aerial vehicle launchers, tanks, large artillery pieces and other vehicles.

The report said that although no TELs or mobile-erector-launchers for the North’s larger intermediate-range or intercontinental ballistic missiles have yet been observed, those “would likely remain hidden” under shelters “until the day of the parade,” which is scheduled for Sept. 9.

The group also said that the number of shelters at a heavy equipment storage area used to house and prepare the military vehicles for the parade had increased since Aug. 12, “indicating next month’s parade will likely be considerably larger than the military parade earlier this year.”

The North has refrained from missile and nuclear tests this year, and even toned down the earlier parade in February.

That could change after U.S. President Donald Trump’s surprise announcement Friday canceling a planned visit to North Korea by Secretary of State Mike Pompeo in the coming week. Trump cited insufficient progress in negotiations for Pyongyang to relinquish its nuclear weapons as the reason for the trip’s cancelation.

In February, South Korea’s Yonhap news agency reported that as many as 50,000 people gathered in Pyongyang’s Kim Il Sung Square to watch that parade, which included around 13,000 soldiers.

While much of that parade was standard fare, it was the event’s climax, with the appearance of North Korea’s missile force, that drew the greatest attention.

The stars of that show were four Hwasong-15 long-range ballistic missiles, and several Hwasong-14 long-range missiles, as well as Hwasong-12 and Pukguksong-2 intermediate-range missiles.

The Hwasong-15 made its debut in November last year and is believed capable of traveling more than 13,000 km (8,000 miles), which experts say puts much, if not all, of the United States within striking distance.

It was the first time that multiple examples of the Hwasong-15 had been seen together.