Sauber boss Monisha Kaltenborn has admitted that the Swiss team thought about entering the all-electric single-seater series Formula E.

Formula E is reportedly going from strength to strength, with Audi, Mercedes and BMW set to join Jaguar and Renault in the capital city-based street category.

It might be said that Formula E is now a genuine threat to a series like DTM, given the future involvement of all three German manufacturers.

"No, we are not concerned," DTM boss Hans Werner Aufrecht told DPA news agency.

"All three manufacturers have made a clear commitment to DTM, and in what form their motor sport programmes are designed is for them alone."

According to Brazil's UOL, Sauber F1 chief Kaltenborn admitted at Suzuka that the Swiss team have been interested in Formula E "from the start", and the "door is still open".

"We had other [financial] problems to solve and we did not need a new one," she added. "But we will continue to look at it carefully."

Kaltenborn said that it is interesting that two companies in US media tycoon John Malone's Liberty empire are now shareholders in F1 and Formula E respectively.

"So they seem to find some synergy, although from a different perspective, but why should it not work for a team as well?" she wondered.

However, Kaltenborn admitted that potentially skyrocketing costs in Formula E could become a problem, given the influx of major car manufacturers.

"It will be interesting to see how this develops, which could take five or six years or perhaps just two, we'll have to see what happens," she said.

Sauber have yet to pick up a point in the 2016 F1 championship.