PITTSBURGH, May 17 (UPI) -- A report published Saturday said United Airlines is balking at the terms of a possible merger between it and US Airways of Pittsburgh.

The Pittsburgh Post-Gazette quoted sources close to the negotiations as saying "most" of the uncertainty surrounding the merger talks was coming from United, which has yet to agree with US Airways on such issues as where the headquarters of the combined operation would be and who would make up its management team.

The newspaper said its source confirmed "both sides have been engaged in conversations for the last two months" and that while US Airways "appears ready to work out the details, United could still decide to remain independent." While no formal timetable has been set for the merger, negotiators expect United could make a decision by the end of May, the newspaper said.

However, the Post-Gazette reported that concern is high among the two airlines that the longer the discussions drag on, the more likely the deal will draw tough antitrust scrutiny from Congress.