The military branch's 10th Wideband Global Satellite Communications platform was assembled onto the ULA rocket at Cape Canaveral Air Force Station in Florida after being fuelled with maneuvering propellants at a facility in Titusville.
Cape Canaveral teams now expect to verify Delta 4 and WGS 10's electrical and mechanical connections while conducting readiness reviews and countdown exercises over the next few weeks.
Delta 4 will carry WGS 10 until it reaches elliptical geostationary transfer orbit and head toward an operating post over 22K miles above the equator.
WGS 10 will be a part of a military satellite fleet designed to transmit classified and unclassified data in X-band and Ka-band frequencies between U.S. and allied forces worldwide as part of a potential 14-year mission.
The upcoming launch will serve as Delta 4's second flight of 2019, with another single-core Delta 4 rocket carrying a GPS navigation satellite slated to lift off from Cape Canaveral in July.