The battle for Dollar Thrifty is likely to be a lengthy one between the second largest rental firm in the US, Avis, and the nations third largest, Hertz. Last month Hertz offered $1.2 billion for the budget brand.

Avis then stepped in with the announcement that it would also like to buy Dollar Thrifty, and although no formal offer has been made, Avis said that it is likely to offer substantially more than Hertz’s $41 per share deal. Dollar Thrifty’s share price is currently at $45.45.

However, money is not the only concern. Although experts predict that Dollar Thrifty will go for the highest offer, both Avis and Hertz still need to persuade anti-trust regulators that they will not be harming competition by purchasing the budget car hire firm.

Hertz is arguing that because it is a pricier, more premium brand than Dollar Thrifty, there would be no conflict of interests, as Dollar does not primarily target the business market. Avis are likely to say that this is not a strong argument, because Hertz is known to target budget customers by offering cheap deals on the web.

Both firms have submitted their applications for takeover approval with the Federal Trade Commission. McDermott, Will & Emery antitrust lawyer, David Marx, said that regulators would be looking at whether there was the potential for prices to rise after a merger. If this looks like being the case, then assets may need to be divested, or a merger could be blocked on the grounds that it would be unfair for competition.