The Delta 4 rocket enclosed within the mobile service tower at pad 37B. Photo: Boeing

The inaugural flight of Boeing's Delta 4 has been postponed from the end of August to around October 9 because testing of the brand-new rocket is running behind schedule at Cape Canaveral's rebuilt launch pad 37B.

"As we have worked through some of the processing, we got to the point where we needed another month," Boeing spokesman Walt Rice said Monday.

"Some things take longer than anticipated, which is to be expected with a new launch vehicle."

The company had requested a new launch date in late-September from the Air Force-controlled Eastern Range, which is the vast network that provides tracking, communications and safety services to all Cape rocket flights. But the next available slot wasn't until October 9.

Assembled in a nearby hangar, the rocket was rolled horizontally to the launch pad on April 30 and erected upright to begin a multi-month series of tests and rehearsals in preparation for the maiden liftoff.

A pretend satellite payload, already encapsulated in the rocket's nose cone, has been hoisted atop the rocket to give workers the chance to check out handling equipment and the procedures of attaching spacecraft to the launch.

However, technicians have not yet started a sequence of fueling exercises in which super-cold liquid oxygen and liquid hydrogen will be pumped into the rocket. The tanking tests were originally envisioned to begin last month.

After the fueling tests are completed, the team will conduct two countdown dress rehearsals to simulate what launch day will be like. The second demonstration will conclude with a brief ignition of the rocket's RS-68 main engine.

The Delta 4 will carry Eutelsat's W5 telecommunications satellite into orbit.