Lotus CEO Matthew Carter says he remains confident that Renault will follow through with its plans to purchase the Enstone squad ahead of the 2016 campaign.
Renault signed a letter of intent in September to assume control of the team which it ran between 2002 and 2009, during which period it claimed the world championship twice.
A deal between the parties has yet to be completed but Carter is sure that the situation will be successfully resolved.
"Renault issued a letter of intent, so behind the scenes the Renault and Lotus senior management are working flat out to make sure that we get the deal done," Carter told the official F1 website.
"Things are progressing, but these things take time. I am confident that the deal is going to happen, but as I said, it needs time to get it across."
Carter says that Lotus still has two design options in case the Renault deal does not go through.
"We have two options for an engine next year: either we go with Mercedes or Renault. We are progressing along that route. We’ve got two designs for next year’s car and we are pushing forward with both options."