The U.S. Air Force is unlikely to reach an agreement with Lockheed Martin Corp before the end of the year about a multibillion dollar purchase of new military communications satellites, a top Air Force acquisition official said.

Lieutenant General Charles Davis, the top military official in charge of Air Force acquisition, said the two sides still had "a little bit of work to go in negotiations" about the fifth and sixth Advanced Extremely High Frequency (AEHF) satellites, making it unlikely that a deal could be struck before year-end.

"We will not obligate the funds until we are sure ... that we have a fair deal for us and Lockheed," Davis told Reuters in an interview. "I don't think the plans get us to an award on that before the end of the year."

(Reporting by Andrea Shalal-Esa; Editing by Phil Berlowitz)