ATLANTA (AP) — UAL Corp.'s United Airlines and Delta Air Lines Inc. have been discussing a combination between the nation's second- and third-largest carriers that would keep the United name and the corporate headquarters in the Chicago area, The Associated Press has learned.

There is a sense of urgency in the talks, which have been going on for some time and continued as recently as a week or so ago, an official with knowledge of the talks said Wednesday. The official spoke on condition of anonymity because the person was not authorized to speak publicly.

''They want to get something done before a new administration gets in and so they get the clock ticking on'' federal regulatory approval, the official said.

The exact financial details of the transaction being discussed are not clear. But the talks involve United being the name of the combined airlines, the headquarters staying in Chicago and Delta's Atlanta hub being an operational center for the two carriers, the official said. One possible scenario involves Delta CEO Richard Anderson being the chief of the combined airline, the official said.

A spokesperson for Elk Grove Village, Ill.-based United did not immediately return a call Wednesday seeking comment. Delta spokeswoman Betsy Talton declined to comment.