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Atletico Madrid are planning to take legal action against Barcelona over their pursuit of Antoine Griezmann, according to reports.

El Larguero, a radio show broadcast on leading Spanish station Cadena SER, has reported that the Wanda Metropolitano club will escalate their complaints against their La Liga rivals.

Griezmann, who opted to stay at Atletico Madrid last summer after a drawn out transfer saga, announced his intention to leave the Spanish capital in a video message last month.

Although a move to Barcelona has not yet been confirmed, it is expected he will make the long-awaited switch to the Nou Camp.

It has now been claimed that Griezmann started negotiating with the Catalan giants way back in November and signed a deal in March - before Atletico Madrid had been knocked out of the Champions League by Juventus .

It is alleged that Atletico Madrid have documentary evidence to prove that to be the case, prompting them to take steps to study the information and determine how it can take formal action.

(Image: AFP/Getty Images)

Griezmann penned a big-money contract extension last summer which included a €200m release clause.

But that figure is set to drop to €120m as a result of a further clause in the deal on July 1, at which point Barcelona are expected to formally sign the French star.

The move has recently been thrown into some doubt amid reports Barcelona stars have looked to veto the move having been unhappy with Griezmann's conduct last summer.

(Image: REUTERS)

And it seems Atletico are now also unhappy with how the saga has unfolded given he negotiated with their rivals at a time when their campaign was still well and truly alive.

With concerns the Barcelona move could fall through, Manchester United are amongst those said to be on red alert and monitoring the situation with a view to a move.