The rocket is to be launched by the Russian-American joint venture International Launch Services (ILS) from the Baikonur space center in Kazakhstan.
"An on-board computer failure was discovered in the Breeze M booster during prelaunch testing. Although the computer has been replaced, extra time is needed to test it. For this reason the launch has been rescheduled for August 19," the space agency representative said.
The Inmarsat-4 satellites, built by EADS Astrium, are among the largest and most sophisticated commercial communication satellites in the world, and are capable of delivering advanced voice and broadband data communications to mobile users.
ILS provides satellite customers with a complete array of services and support and has exclusive rights to market the Proton, Russia's premier heavy-lift launch vehicle, to commercial satellite operators worldwide.
The Khrunichev State Research and Production Center, which has a majority interest in ILS, is one of the cornerstones of the Russian space industry. Khrunichev manufactures the Proton system and is developing the Angara launch system.