A wiring issue has apparently delayed NASA's plan to roll the space shuttle Discovery over to the massive Vehicle Assembly Building (VAB) in Florida next week.

NASA space shuttle officials had hoped to roll Discovery out of its Orbital Processing Facility (OPF) and into the VAB on March 22, where its external tank and solid rocket boosters already stand assembled.

But in a status report released Friday, NASA officials said additional work was needed to address wiring issues in Discovery's payload bay and landing gear doors. Shuttle officials now hope the orbiter will be ready to roll out of the OPF between March 26 and March 28.

Shuttle engineers apparently first spotted the wiring issue on Discovery's sister ship Endeavour. Fasteners were found to be chafing tubing around the wires, leading technicians to inspect Discovery's wiring as well. Those inspections are now complete and engineers are expected to remove some wire trays aboard Discovery and install chafe protection in upcoming days, the status report stated.

Discovery's STS-114 mission is slated to be NASA's first shuttle to fly since the 2003 Columbia accident. The mission has a current launch window stretching from May 15 to June 3.

Despite the wiring delay, STS-114 mission managers are still targeting that launch window, NASA spokesperson Jessica Rye told SPACE.com. It should take about seven days to attach Discovery to its external tank and solid rocket boosters once the orbiter arrives at the VAB, she added.

NASA officials have repeatedly stressed that their return-to-flight operations are driven by reaching mission milestones rather than adhering to a schedule. Discovery's roll over to the VAB, and subsequent roll out to the launch pad, are among the mission's next major milestones.

Other upcoming milestones include the hatch closure for Raffaello, a payload bay-mounted cargo container that Discovery will deliver to the International Space Station (ISS). That hatch closure is currently set for mid-April, NASA officials said.