McCartney, 65, and 39-year-old former model Mills are currently locked in a High Court divorce battle which is also being played out across the pages of Britain's newspapers.
McCartney and Mills are both using the same divorce lawyers used by Prince Charles and the late Princess Diana, Fiona Shackleton and Anthony Julius.
"It could well go to trial because they are both quite stubborn," an unidentified lawyer was quoted as saying by The Times.
The paper reports that McCartney had offered 20 million pounds ($46 million) to Mills as a settlement, with Mills replying that she will accept a sum of 50 million pounds ($117 million).
The couple have a three-year-old daughter, Beatrice. © 2007 Australian Broadcasting Corporation
