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.