Hertz has raised its offer for Dollar Thrifty to $1.43 billion (£930 million) in cash and shares in the latest stage of a bidding war with rival Avis.
Hertz had earlier agreed to buy Dollar Thrifty for $1.1 billion. But the Hertz offer agreed in April was trumped by Avis, which raised its rival bid for Dollar Thrifty to $1.36 billion.
However, Dollar Thrifty had raised concerns that the Avis bid may run foul of US anti-trust regulations. Avis has also refused to include a fee if it cannot complete its proposed merger.
A vote on the Hertz deal has been postponed from Thursday (September 16) to September 30 following the revised offer.
Dollar Thrifty earned revenues of $1.55 billion last year mainly from leisure travellers while Hertz made half of its $7.1 billion from business travellers. The takeover would help Hertz increase its share of the tourist rental sector.