Dr Helmut Marko says Red Bull’s focus has "clearly" switched to 2019.
The energy drink owned team started the year with championship ambitions, but key official Marko admitted that Mercedes and Ferrari have raced ahead.
"The euphoria has given way to reality," Dr Marko told Kronen Zeitung newspaper. "We have fallen behind Mercedes and Ferrari.
"We want to end the year as well as possible, but our focus is clearly on 2019."
Next year, Red Bull will switch to works Honda power, and Marko said the entire team is "optimistic".
"We are seeing an extreme commitment and great energy from the Honda side," he said. "And our side as well, of course.
"After Singapore, some of our leading people flew to Tokyo where the exchange of ideas is intensifying. It’s the first time Red Bull has had an engine manufacturer behind us."
He said McLaren’s troubles of 2015-2017 don’t worry him, as the progress at the junior team Toro Rosso this year has been "obvious".
"Honda’s headquarters is 15 minutes from us. In the past, we were just waiting to see what Renault’s plan was but now everything is focused on us," Marko explained.
"We have good numbers from the factory so far and Honda is enjoying the benefit of insight from four cars. The (2019) car will be ready on time," he announced.
"We want to be competitive right from the start and drive for victories. Whether it’s enough for the title I cannot say now, but our target must always be this."