Sauber's Felipe Nasr expects Haas to be a threat in debut F1 season

Haas has entered F1 with strong ties to Ferrari and is understood to have a decent midfield budget.

Fellow Ferrari customer Sauber has struggled financially in recent seasons and its new car will not make its debut until next week's final pre-season test at Barcelona.

Nasr says rival teams have all progressed and that Haas is likely to be in the midfield mix too, even though it is a brand new team.

"With the resources and financial side they have they can catch up very quickly, they can develop very quickly," Nasr said.

"It's difficult for a new team to start a season in F1, to get the operations side correct, to get everything smooth, but I'm sure with time they will be very competitive."

Although Sauber has been unable to run its new car at this week's opening test, Nasr said the Swiss team has still completed some useful running with its 2015 car.

"There are many other things you can do," he added.

"We all wish the new car was ready before, but areas we didn't have time to explore last year we did it now.

"By running the old car we've had good days practicing our communication and procedures.

"It might sound boring, but we know the radio communications will be much more restricted this year, so it's good to practice them.

"Set-up work [too], they are all valid and worth doing.

"We really have a read on the tyres as well.

"By running the same car we had last year we know the references.

"It gives us an idea what to expect. It [the test] was valid."