Developer Otary has lined up Siemens Gamesa to supply turbines totalling more than 500MW to the Mermaid and Seastar projects off Belgium.
The German-Spanish company is the preferred bidder "after intensive discussions with multiple suppliers" and will supply 58 turbines, Otary said.
Hardware will feature 167-metre rotors but the power rating has not been revealed.
Both sides are continuing contract negotiations and aim to reach an agreement on the terms and conditions of turbine supply as well as service and maintenance before the summer.
"We are pleased to do this announcement as this will trigger a sequence of events that will eventually lead up to the construction of two offshore wind farms with a total capacity of around 500MW," said Mermaid chief executive Mathias Verkest.
"In order to reach project completion by 2020 the support mechanism announced by the government still has to be transposed into legislation, but we are confident the Belgian government will do its utmost to make this happen in the next weeks based on the principles agreed in October 2017."
The port of Ostend is also expected to play a significant role as a construction hub for the projects, Otary said.
The around 300MW Mermaid and 246MW Seastar are due online in 2020.
Image: Siemens Gamesa