Sauber needs some more sponsors to ensure the C29 car can be properly developed, Pedro de la Rosa insists.

Sauber needs some more sponsors to ensure the C29 car can be properly developed, Pedro de la Rosa insists.

Four races into the 2010 season and still with a mainly blank white livery, the formerly BMW-owned team is struggling with poor reliability and lagging pace.

Team boss Peter Sauber insists the team has a guaranteed budget to survive the 2010 season.

But when asked about Sauber's sponsorship situation, de la Rosa told the Swiss newspaper Blick: "This is a very important point.

"With each day it is more difficult to find backers for 2010, but without finances a normal development of the car is hardly possible," said the Spaniard.

Asked about the car's main problems, he answered: "There have been too many engine problems, and at the rear of the car something is not right -- it is too unstable.

"We simply must believe in our abilities and those of our new technical boss James Key. And also that luck might be with us sometimes as well."

De la Rosa returned to a full time racing role in 2010 after several years as McLaren's test driver, and it is already rumoured that Sauber is considering replacing him with a pay-driver on the basis of his initial form.

He admits it has been a trying campaign so far.

"I knew that with Sauber, difficult work was awaiting me. But after the tests in February I didn't think it would be quite so hard."

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Sauber needs sponsors to boost 2010 car - de la Rosa