US Airways said it would raise its offer by $1.7 billion from its Nov. 15 bid that was currently valued at $8.5 billion.
The increased offer comes just two weeks after the chief of Tempe, Ariz.-based US Airways, Doug Parker, told The Associated Press that his company had no intention at the time to increase its offer.
Even so, Parker did not exactly rule out the possibility of changing his mind about the price.
"If these conversations move to negotiations about value, we're happy to have those conversations," Parker said in the interview.
In a statement Wednesday, Parker said US Airways was raising its bid to remove any doubt that its bid was worth more than Delta's plan to remain a standalone carrier.
"It is time for this process to move forward," Parker said. "We continue to believe that this is the right time to create a better airline that provides more choice to consumers, increased job security for both airlines' employees and generates more value for all of our stakeholders."
Delta spokeswoman Betsy Talton said the airline had no immediate comment.
US Airways said the increased offer is set to expire on Feb. 1 unless creditors indicate support for the start of the due diligence process, which would open up Delta's books to US Airways. US Airways also wants Delta to postpone a Feb. 7 bankruptcy hearing involving its reorganization plan.
The increased bid amounts to 89.5 million shares of US Airways stock and $5 billion in cash. The original offer included 78.5 million shares of US Airways stock and $4 billion in cash. The value of the increased bid could go even higher if US Airways' stock rises after the market opens later Wednesday.
Executives of Atlanta-based Delta have said they oppose a buyout by US Airways. The nation's third-largest carrier has filed a reorganization plan that calls for it to emerge from bankruptcy by the middle of this year as a standalone company worth $9.4 billion to $12 billion.
Based on the Delta's valuation method, US Airways estimated that its increased bid could actually be worth $12.7 billion to $15.4 billion.
Despite the position by Delta management, Delta's unsecured creditors committee in its bankruptcy case will play a key role in deciding the airline's future course. The committee had said prior to Wednesday that it was reviewing both Delta's standalone plan and US Airways' buyout offer.