International Combustion, the Derby-based boilermaker, could be sold within six to eight weeks in part or as a whole. It was put up for sale by Rolls-Royce last July.
More than one buyer is said to be interested in the company, which sells boilers and combustion systems to power stations.
Trade unions expect a purchase to include all of International Combustion, which has one site at Derby employing 890 staff.
Rolls-Royce said it was confident of making a sale, but it was discussing options with different buyers, which might include breaking up the company.
Union officials were dismayed that a buyer might not be able to save 100 jobs expected to go in a month’s time.
At the end of February 180 workers were given a 90-day redundancy notice. This follows 150 redundancies since the sale was announced.