FRANKFURT, May 21 (Reuters) - Germany's premium automakers Mercedes, Audi and BMW have teamed up with private equity firm General Atlantic to raise their chances of clinching Nokia's map unit HERE by overtaking Internet bidders, two people familiar with the matter said.

One financial industry source said on Thursday that General Atlantic would likely take a 30 percent stake in the auto industry-led consortium, but that the exact percentage had not yet been finalised and could change.

A separate source said that each of the three carmakers was prepared to chip in up to 700 million euros ($780 million) but that the percentage stakes of each manufacturer was not yet fixed.

The automakers have not heard back from Nokia and are waiting for a response before they weigh whether to top up their bid, another person said.

Nokia, Mercedes-Benz parent Daimler, BMW and Volkswagen's Audi declined to comment. Greenwich, Connecticut-based General Atlantic Partners also declined to comment.

($1 = 0.8974 euros) (Reporting by Edward Taylor and Arno Schuetze; additional reporting by Andreas Cremer; Writing by Eric Auchard; Editing by Maria Sheahan)