The two firms are competing for the study's environmental assessment contract. Consultant Parsons Brinckerhoff is understood to be favourite.
The Department for Business Enterprise and Regulatory Reform (BERR) study will examine options for harnessing tidal power in the Severn Estuary.
The study will focus on the construction of a tidal barrage between Cardiff and Weston-Super-Mare.
BERR Severn Tidal Power Feasibility Study deputy director Gary Shanahan said the department was close to appointing consultants for the Strategic Environmental Assessment and for a contract to establish the financial feasibility of various options.
NCE will be running a detailed update on the barrage project next week.