He said that fuel inflation and other factors outside of the department's control were responsible for three-quarters of the cost increase over the past year.

BBC: Watchdog warns of defence project delays and overspending

Santorum advisers including Gidley said the final decision to suspend the campaign, which allows him to continue raising money and probably keep control of delegates won so far, came Monday night and was based on three factors.

CNN: Santorum suspends campaign, clearing Romney's path