Bayern Munich have angered Borussia Dortmund chiefs with their signing of Mario Gotze.
The Bundesliga champions confirmed today the attacking midfielder would join them on July 1 after they agreed to meet the release clause in his contract.
But their apparent lack of contact with the selling club over the deal has upset Dortmund, who earlier revealed Gotze's agent had informed them the 20-year-old wanted to move to the Allianz Arena, but stressed they had heard nothing official from the Bavarians.
In announcing the deal, Bayern claimed they had kept quiet "out of consideration" for Dortmund's Champions League semi-final with Real Madrid tomorrow night.
Dortmund pointed out that Gotze acted appropriately at all times.
Gotze was under contract at Dortmund until 2016, with his release clause reportedly set at 37 million euros (£31.5m), meaning he will become the most expensive German player of all time.
Dortmund chief executive Hans-Joachim Watzke said on the club's website: "We are obviously disappointed beyond measure, but emphasise that both Mario and his advisors have behaved within the terms of the contract."
The timing of the announcement is certainly far from ideal for Dortmund, coming just a day before their first-leg meeting with Jose Mourinho's Madrid.
But the club have asked for fans to support Gotze and the rest of the players as they seek a place in the Wembley final against Bayern or Barcelona.
A Dortmund statement said: "Coach Jurgen Klopp and sporting director Michael Zorc asks all fans of Borussia Dortmund to support Mario Gotze unconditionally as they would any other player in the final games of the season, but especially in the important Champions League semi-final against Real Madrid."
Losing Gotze, especially to their closest domestic rivals, would be a huge blow to Dortmund.
Klopp's side recently relinquished the Bundesliga title they won in each of the past two seasons with Bayern winning the 'salad bowl' in record time.
Gotze has emerged as one of the most coveted players in European football since coming through the ranks at Dortmund and making his Bundesliga debut in November 2009.
He played a key role as Dortmund won back-to-back Bundesliga crowns and has made 22 appearances for Germany, scoring five goals.
In January, Bayern announced former Barcelona coach Pep Guardiola will succeed Jupp Heynckes as boss this summer, having signed a three-year deal.