FAR 42.1302 -- Suspension of Work.
A suspension of work under a construction or architect-engineer contract may be ordered by the contracting officer for a reasonable period of time. If the suspension is unreasonable, the contractor may submit a written claim for increases in the cost of performance, excluding profit.
FAR 52.242-14, Suspension of Work, gives the Government this right.
FAR 42.1303 -- Stop-Work Orders.
(a) Stop-work orders may be used, when appropriate, in any negotiated fixed-price or cost-reimbursement supply, research and development, or service contract if work stoppage may be required for reasons such as advancement in the state-of-the-art, production or engineering breakthroughs, or realignment of programs.
FAR 52.242-15, Stop-Work Order, gives the Government this right.