A final decision about gearboxes for 2021 has not been made.
"There is this proposal, but nothing has been decided about the technical regulations yet," he told Sky Italia.
"It is a test to see if a standard part costs less. The idea is to see how much it costs and compare that with what we spend at the moment.
"But there is nothing yet in the regulations," Steiner added.
Haas currently buys its gearbox from Ferrari.