National Harbor, Maryland – An unresolved discrepancy in cost estimates between the Air Force and the Office of the Secretary of Defense over the next-generation intercontinental ballistic missile replacement will not keep the program from moving forward, the secretary of the Air Force said Tuesday.

Deborah Lee James told reporters at the Air Force Association conference that the delta between the cost estimates for the Ground Based Strategic Deterrent (GBSD) program is "not that high" and indicated she was not surprised by the difference in numbers, given how long it has been between the last ICBM program and its replacement.

"We haven't done this in 40 years. There were different approaches used to build up the costs," James said.

Click here for our coverage of the 2016 Air Force Association conference.   

In the short term, the Air Force and OSD's cost assessment and program evaluation (CAPE) office will compute, potentially with input from Deputy Defense Secretary Bob Work, the funding needed to keep the program moving forward in the fiscal 2018 budget request, which is currently being formulated inside the Pentagon.

In the longer term, James is confident a more accurate cost estimate will come when industry submits their offers in late October. Lockheed Martin, Northrop Grumman and Boeing are all expected to make bids on the GBSD program, with a down-select to two companies planned for late 2017.

"We are not going to know with better certainty until after we get the information and it comes back from industry on the [requests for proposals]. We believe that will provide some additional insights to ultimately refine these cost estimates, and with that refinement can come a new service cost position at some point in the future," James said.

"So we're going to do whatever we need to do in order to get through these next few months and settle on whatever we're going to put in the [budget] in the next cycle, but the real issue will be over the next year and beyond we will be continually refining as we learn more from industry and put in better estimates."