NEW YORK (Reuters) — US Airways Group Inc. raised its takeover offer for larger, bankrupt rival Delta Air Lines Inc. by about 20 percent to $10.3 billion yesterday, sweetening a deal for creditors and putting pressure on Delta management.Delta last month rejected the original bid, valued at $8.5 billion at Tuesday’s market close, saying the company is worth at least $9.4 billion, and possibly as much as $12 billion, as an independent carrier.

After making its original bid on November 15, US Airways’ efforts to acquire Delta had stalled with creditors undecided. The latest bid sets a February 1 deadline for creditors to react.

The official creditor committee, which is key to deciding what plan succeeds, and which met yesterday, was not immediately available to comment. The nine-member committee includes Boeing Co., Coca-Cola Co., the Air Line Pilots Association, and the Pension Benefit Guaranty Corp.

A less powerful creditor group that represents some bondholders and other unsecured creditors urged the company to consider the new offer.

“The increased US Airways’ offer merits Delta’s careful attention at this time in keeping with the board’s fiduciary duty to maximise value for Delta’s stakeholders, including members of the Unofficial Committee,” the Unofficial Committee of Unsecured Claim holders of Delta Air Lines said in a statement.

“Only after Delta adequately considers the revised US Airways’ proposal and any other strategic alternative that may present itself, will the members of the Unofficial Committee be in a position to determine whether to support Delta’s stand-alone reorganisation plan,” the committee said.

Delta’s management said it would review the new offer, but said the proposal did not address its past concerns relating to anti-trust and labour issues and the combined company’s debt burden.

“On its face, the revised proposal does not address the significant concerns that have been raised,” the company said in a statement. It noted the new offer would saddle the combined company with an additional $1 billion in debt.

Delta also is looking for alternatives and has been talking for weeks with fellow bankrupt carrier Northwest Airlines Corp. about a possible link-up that could be an alternative to the US Airways offer, the Wall Street Journal reported yesterday, citing people familiar with the matter.

Delta and Northwest declined to comment.

Analysts and industry watchers expect other mergers in the industry to hinge on the success of US Airways’ bid for Delta. The increased offer boosts its prospects.

“This would seem to be an irresistible offer,” airline consultant Robert Mann said. “I think Delta’s stuck. I think they’ve kind of cornered themselves.”

A raised bid was expected after US Airways on Monday bolstered the financial muscle behind its effort by adding Morgan Stanley as a backer alongside Citigroup. The two banks have committed $8.2 billion in financing for the offer.