Renault has warned Red Bull that it will not offer an extension to the FIA's May 15 deadline for a 2019 engine deal, giving the former world champions less than two weeks to make a decision on its power unit supply for next year.
Red Bull faces a straight choice between renewing its contract with Renault or teaming up with Honda next year, and held its first formal talks with the Japanese manufacturer at the Azerbaijan Grand Prix last weekend.
Current estimations put Renault's engine ahead of Honda's in terms of power output, but both remain some way short of class leaders Ferrari and Mercedes.