Madonna and Guy Ritchie are set to divorce.

The couple are set to imminently announce they are separating, and reportedly want their divorce to be finalised by Christmas - which would be their eighth wedding anniversary.

A source told Britain's The Sun newspaper: "It's very sad. They were a great couple and brilliant parents. They just couldn't live together any more.

"Despite huge attempts to patch things up they both knew deep down that divorce was on the cards. It wasn't a matter of 'if' but 'when'. They tried hard over the last few months but their arguments were getting out of control."

US singer Madonna, 50, and British film director Guy, 40, are believed to have been clashing about their respective careers and Madonna's desire to adopt a second child, a move Guy is opposed to.

While the '4 Minutes' singer was keen to wait until next year to announce the split - after her current 'Sticky and Sweet' tour has finished - Guy is said to have demanded the split be made public now.

The source continued: "The final straw came before Madonna started her US tour. She wanted a highly stage-managed separation, with their split being announced when it was convenient for her.

"But a series of rows around Guy's 40th birthday last month were so bad that Madonna ended up storming out of the house, and Guy's had enough. He said if they were going to split, it has to be now — and their marriage will be over in a matter of weeks.

"Madonna was dithering at first about whether a separation would be best or whether to go ahead with the divorce. She has now agreed with Guy that a divorce is the best thing to do."

Guy is said to have halted shooting on his latest film project, 'Sherlock Holmes', and flown back from France to announce the news to his parents. He is expected to move out of the couple's home in Marylebone, London, owned by Madonna and into Ashcombe House, the Wiltshire property which belongs to him.

Rumours Madonna and Guy's marriage was crumbling have dogged the couple for months.

In July, it was initially reported they were heading for divorce, and the whispers intensified after Madonna was accused of having an affair with married baseball player Alex Rodriguez.

Guy flew out to see Madonna in New York in July in an attempt to patch things up and the couple put on a show of strength for the London premiere of Guy's latest film 'RocknRolla' in September. They were also together at Madonna's 50th birthday, but then Madonna left Guy's own birthday party last month after just an hour.

Madonna and Guy have also reportedly been fighting over their children - son Rocco, eight, their adopted son David Banda, two, and Lourdes, 12, the pop star's daughter with Carlos Leon.

The 'Snatch' filmmaker wants the children to stay rooted in one place, rather than being constantly moved around with their mother.

Madonna's representatives have so far declined to comment on the divorce claims.