FRANKFURT, July 29 (Reuters) - Volkswagen (VOWG_p.DE) boss Herbert Diess on Thursday dodged questions about a potential initial public offering of Porsche AG, saying only that any steps to tap capital markets would have to be carefully considered. "As I said, we continue to review our set up. First priority is now to finance the battery ramp-up where we try to partly externally finance and we are working out the models," Diess told analysts after presenting first-half results. "And all the other, let say, possibilities to go to market, which might be trucks, where we could dilute a little bit ... or any other things, we have to consider." Volkswagen still owns 89.72% of Traton (8TRA.DE), the trucks unit it listed in 2019. His remarks came a day after Volkswagen unveiled a bid to buy Europcar jointly with Attestor and Pon Holdings via vehicle called Green Mobility Holding. Volkswagen will hold two thirds of the bid vehicle, with Attestor owning 27% and Pon Holding 7%. Volkswagen said that its stake in the vehicle will mean that it will contribute 1.688 billion euros ($2.01 billion) to the offer if it passes a 90% acceptance threshold. ($1 = 0.8418 euros)