The contracting and negotiations component ends with the elements of managing the contract/PO. At this stage the supply manager needs to be involved in tracking and ensuring that the supplier does what is agreed to in the negotiated contract. It is not merely "checking on the supplier" but trying to see that the supplier is on board and is providing goods and services that meet the expectations of internal customers like say production and also external customers like say the Government who might be using the equipment supplied that has a critical component from the supplier under contract. Responsibilities at this stage also include the need to step in if costs of the supplier go out of control and a price adjustment becomes necessary. Also responsibility is pretty overall including the need to meet supplier's payment schedules as agreed in the contract. Finally the contract might need a "closeout" that is concluded or might need to be terminated for cause or convenience.
In other words "contracting and negotiation is a lot more than mere negotiations which is always the hottest seminar topic in supply manager training materials and events.