After winter testing, the general consensus is that Renault and Haas will battle to lead the midfield behind top teams Mercedes, Red Bull and Ferrari.
However, team advisor Prost says that Renault's goal is only to improve.
"In 2018 we will progress and gradually become stronger," he told Nice Matin newspaper at a Formula 1 demonstration in Nice.
"Theoretically, the top three teams retain a great advantage and it will be difficult to catch them.
"But by the middle of the season we will have new parts and you can never exclude the possibility of being on the podium."
However, Prost said that targeting victories is not yet on Renault's agenda.
"I think it's pointless to name specific goals, because in motor racing it doesn't work like that," he said.
"The team is continuing to restructure, many new employees are appearing and the Enstone factory is improved. Soon the same will happen in Viry.
"When will our efforts be rewarded - tomorrow or the day after? It's still too early to say. First, let's see what progress we make this year."
"Judging by the winter tests, Lewis has a slight advantage. Very small," he said.
"But it's a long season - 21 races. Anything can happen and surprises are possible. In my opinion, Red Bull is very competitive as well."
The season begins on March 25 with the Australian Grand Prix.