Dimitar Berbatov's days at Old Trafford may be coming to an end this summer. Reuters

Manchester United striker Dimitar Berbatov is free to negotiate a move to another club next month because Sir Alex Ferguson is yet to decide whether or not to keep the mercurial Bulgarian.

According to The Times, Berbatov is out of contract at the end of the season and Manchester United are yet to take up their option on a "one-way" clause to retain the striker who turns 31 next month.

As a result the languid Manchester United star is free to begin discussing terms with any prospective suitors in January but Ferguson is free to exercise that clause whenever he wishes between now and the end of the season.

The aforementioned source intimates Berbatov could feasibly be openly negotiating a possible deal with a Premier League rival, only for Manchester United to then opt to keep their record signing.

Berbatov has regularly stated his desire to remain at Manchester United for the remainder of his career despite his increasingly peripheral role at Old Trafford.

The Premier League's joint top scorer last year has been increasingly overlooked by Sir Alex Ferguson this season, with Danny Welbeck, Javier Hernandez and Wayne Rooney his preferred options up front.

Berbatov is currently making his way back from injury but the uncertainty surrounding Federico Macheda and Mame Biram Diouf and the perpetual absence of Michael Owen, has heightened the prospect of Manchester United retaining the former Spurs talisman.

Omitted from last season's Champions League final squad, Berbatov has enjoyed a Manchester United career of stark contrasts. Occasionally unplayable, his hattrick against Liverpool last season displayed his genius, but more often than not underwhelming, Berbatov has never quite displayed the type of patent talent he has in abundance on a consistent basis.

He has started just one Premier League match all season and has endured a frustrating time with injury of late and his future at Manchester United remains open to debate at this juncture in his unpredictable career.