Sauber will use year-old Ferrari engines for 2017 F1 season

Next year's F1 cars will sport wider bodywork and tyres, both of which will contribute to increased cornering speeds and significantly reduced lap times.

There was delay in reaching an agreement on the 2017 aerodynamic and engine rules, so Sauber boss Monisha Kaltenborn chose to make a call early in the year to stick with Ferrari's 2016 power unit.

"The prime reason for it was that we really wanted to have the ability to focus more on the chassis development," she told Autosport.

"This decision was taken when the rules were not 100% sure.

"We decided to go this way in the early part of the year, to be sure that if last minute changes come up we can react to them while focusing on chassis development."

The early decision came at a time when Sauber was searching for new financial backers, but Kaltenborn said that did not influence the decision.

Toro Rosso, known to have one of the best chassis on the grid, ran a one-year-old spec Ferrari unit this year, and while the team was competitive early on, it's form took a big dip a third of the way through the campaign.

There is an argument that as Formula 1 enters a fourth year with stable engine regulations, the gains manufacturers could make may be smaller and the disadvantage of having a unit that is undeveloped would be reduced.

However, engine development will be completely unrestricted after this year, which means engine manufacturers could potentially make bigger strides in-season.

When asked if she was concerned by Toro Rosso's struggles with an old engine, Kaltenborn said: "It's not a worry, it's a challenge.

"We don't know what their reasons are. We have to look at our situation.

"We have a development plan in place for next year, which comprises the updates we want to be able to reach the position we are targeting.

"I don't see why that shouldn't work."

Sauber chose not to run the latest 2016-spec Ferrari engine introduced at September's Italian Grand Prix, but it will get that iteration from the start of next season.

Kaltenborn said Sauber remains on course to have a car ready for the first pre-season test that begins on February 27.

She dismissed claims the team is behind with development because it of its earlier search for funding because "planning doesn't cost you anything".