A buyout group including Macquarie Bank said on Sunday it would not extend its A$11 billion ($9 billion) bid for Australia's Qantas Airways beyond May 4, but would speed up payments to shareholders who accepted.
The consortium also said it would allow shareholders who backed the bid to withdraw their acceptances before the offer went unconditional.
The bid group, Airline Partners Australia (APA), is seeking to shore up support for the world's largest takeover bid following a decline in shareholder acceptances last week.
APA eased its offer conditions for Qantas earlier this month after some key shareholders opposed the deal. It now needs 70 percent of shareholder acceptances instead of 90%previously.
The consortium, which also includes private equity firm Texas Pacific Group, said Sunday the offer would not be extended beyond the current May 4 deadline.
"APA is aware that an overwhelming majority of small and large Qantas shareholders support the offer. Now, it is time for those supportive shareholders to accept," APA director Bob Mansfield said in a statement.
"If the bid fails, the share price will almost certainly fall."
However, under Australian law there will be an automatic extension to the offer of 14 days if APA's voting power rises above 50% after April 27, it added.
APA said it would accelerate payments to five business days for shareholders who accepted the bid. It said the change was an incentive for shareholders to accept quickly.
It also announced withdrawal rights to shareholders before the offer is declared unconditional.
The sale of the national icon, dubbed the Flying Kangaroo, met with some political and union opposition but was backed by the Australian government as well as Qantas management.
However, key shareholders who said the A$5.45 per share offer was too low have proved the biggest threat to the deal. Some hedge funds, which hold up to 40% of the stock, are keen to get the offer pushed through.
Qantas shares closed at A$5.36 on Friday.
The bid group also includes Allco Equity Partners, Allco Finance Group and Canadian investment firm Onex.