A source from the defence ministry told news agency Lusa that the tender is open until 23 September.
The management of ENVC's plots, buildings, infrastructure and equipment was recently awarded to the operator of the port of Viana do Castelo.
The port has the right to sign sub-concession contracts with private companies.
These will run until 2031.
Brazilian shipbuilder Rio Nave has been linked to a deal.
The
