NASA officials on Wednesday said the agency would conduct an initial rollout of the massive Space Launch System rocket sometime in March, a multi-week delay attributed to “close-out” tasks that must be completed on the vehicle.

Until this week, NASA had been publicly targeting a February 15 rollout date, when a mobile tower would ferry the SLS rocket from the Vehicle Assembly Building to its launch site at Kennedy Space Center in Florida. Tom Whitmeyer, deputy associate administrator for exploration systems development at NASA Headquarters, said the agency is now targeting “mid-March” for the rollout, but he did not want to set a specific date.

Whitmeyer and other officials on a teleconference with reporters said they wanted to let the teams of NASA employees and contractors in Florida complete their work meticulously rather than being rushed.